Beta

×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Hashing Email Addresses For Web Considered Harmful

timothy posted more than 5 years ago | from the who-has-the-time-to-oh-wait dept.

Privacy 155

cce writes "The MicroID standard, despite getting thrashed soundly by Ben Laurie two years ago, has since been recommended by the DataPortability Project and published on the user profiles of millions of users at Digg and Last.fm. MicroID is basically a hash calculated using a user's profile page URL and registered email address, producing a token that makes the email address vulnerable to dictionary attacks. To see how easy it was to crack these tokens, I conducted a small study, choosing 56,775 random Digg users, and cracking the email addresses of 14,294 of them (25%) using just their MicroID, username, and a list of popular email domains. Digg has more than 2 million users, and that means half a million of them — mostly people who had never heard of MicroID, and had probably not logged in for a long time — had their email addresses exposed to this trivial attack. I also applied this attack to Last.fm (19%) and ClaimID (34%). Digg and Last.fm have since removed support for MicroID, but the lesson is clear: don't publish a hash of my email address online, guys!"

cancel ×

155 comments

Sorry! There are no comments related to the filter you selected.

Solution: salt your emails (4, Interesting)

pwnies (1034518) | more than 5 years ago | (#24786845)

I suppose this is yet another reason why it's nice that a few email services (most notably gmail) allow you to append a string to your email address using the + symbol (e.g. youremail+string@gmail.com will go to the inbox of youremail@gmail.com). In effect it allows you to "salt" your email, which adds a layer of complexity when trying to match these hashes with valid email (not to mention it allows you to check which site compromised your email if you use different 'salts' for each site you use your address on). If more email services start to allow this (doubtful), more sites start realizing that a + in your email is still a valid email (more doubtful), and more users start using it effectively (even more doubtful still), then I don't think the MicroID will be a huge problem.

Re:Solution: salt your emails (5, Insightful)

nblender (741424) | more than 5 years ago | (#24786965)

+ is a bad delimiter. Many web-forms don't accept email addresses with '+' in the username portion. Attempts to educate webmasters to the information in the relevant RFC's is usually met with silence or worse... I did manage to get a FOAF to fix dell.com though.

Re:Solution: salt your emails (2, Interesting)

Rinisari (521266) | more than 5 years ago | (#24787003)

Maybe that FOAF could attack ESPN.com, too. I tried registering there for a fantasy football league at work and used myaddress+espn@gmail.com. The damned system took the + out, making the address invalid!

Postfix Solution (3, Interesting)

bill_mcgonigle (4333) | more than 5 years ago | (#24788187)

Assuming you're using postfix and virtual, you can do something like this:

main.cf:

recipient_delimiter = +
virtual_alias_maps = hash:/etc/postfix/virtual, regexp:/etc/postfix/virtual-regexp

virtual-regexp: /(.*)\-(.*)@example.com/ ${1}+${2}@example.com

and then you can do:

    bob-somesite.com@example.com

this works for every site I've tried but oracle.com, who apparently doesn't want you tracking their mail. :)

Re:Solution: salt your emails (5, Informative)

mi (197448) | more than 5 years ago | (#24788573)

+ is a bad delimiter.

It is the delimiter, originally created as such by the authors of the very first MTA [wikipedia.org] ... There is no other character, that:

  1. Can be part of an e-mail address.
  2. Can not be part of a username.

Many web-forms don't accept email addresses with '+' in the username portion. Attempts to educate webmasters to the information in the relevant RFC's is usually met with silence or worse...

This is, unfortunately, the truth... Far too many programmer wannabees around... It is a good fight, however, and kudos to GMail for keeping support for it (unlike Yahoo! Mail).

I use this whenever I can, when giving my address to web-sites (including Slashdot)...

Re:Solution: salt your emails (1)

profplump (309017) | more than 5 years ago | (#24789823)

"Can not be part of a username" is system-specific (and policy-specific) behavior. I don't allow hyphens, periods, underscores, or numbers in my usernames, and as such they are all valid delimiters.

Depending on the number of users you have, how abusive they are, and how closely you monitor username selection it's entirely plausible to use a delimiter that *is* allowed in usernames, so long as you don't assign usernames that allow abuse.

Re:Solution: salt your emails (1)

synaptik (125) | more than 5 years ago | (#24791269)

Perhaps what we need is an RFC hall-of-shame... when we find websites that don't support the +, add their domain name to the roster.

With enough promotion throughout geekdom, it could become such an embarrassing badge of dishonor that it evokes corrective action... similar to getting RBL'd for relaying spam (except that humans react to it, rather than MTA scripts.)

Wishful thinking?

Just use dots, then (2, Informative)

Cow Jones (615566) | more than 5 years ago | (#24789835)

Apart from the fact "+" is a perfectly valid character in an email address, if you're using Gmail, you can insert random dots in your address, and your mail will still get delivered.

my.name@gmail.com

is equivalent to

my.na.me@gmail.com
my....name@gmail.com
m.y.n.a.m.e@gmail.com
etc

Re:Just use dots, then (1)

Martin Blank (154261) | more than 5 years ago | (#24790391)

Make sure that it's not already in use by someone else. I have two GMail accounts, one for normal mail and one for mailing lists. The only difference between the two is that the second ends in ".ml" which would normally go to the main account, but since I registered the second one, it goes to that completely separate account.

Re:Just use dots, then (1)

Filip22012005 (852281) | more than 5 years ago | (#24790715)

The only difference between the two is that the second ends in ".ml" which would normally go to the main account, but since I registered the second one, it goes to that completely separate account.

I don't get it. Why would username.ml@gmail.com go to username@gmail.com?

Re:Solution: salt your emails (4, Insightful)

Anonymous Coward | more than 5 years ago | (#24787001)

Except that once the salted email is found, everything between the @ and the + will just be discarded.

Re:Solution: salt your emails (1)

bluefoxlucid (723572) | more than 5 years ago | (#24787117)

it's a dictionary attack. mel.hopkins@gmail.com user SugarBaby is Mel.Hopkins ok... mel.hopkins+a83kdZ@gmail.com Okay this is a little harder... we can't just apply names, now we have to apply an exhaustive space search.

superparanoid? regexp (2, Interesting)

Tmack (593755) | more than 5 years ago | (#24787267)

If you are superparanoid, you can run your own mta, like qmail or postfix, and specify your own delimiter to regexp out of the address in one of the pre-processing filters. With qmail, I believe you could even just edit the qmail-smtpd config/run file (iirc, been a while) and add a pipe through sed to do the dirty work with the addy before the normal pipe through qmail.

tm

Re:superparanoid? regexp (1)

19thNervousBreakdown (768619) | more than 5 years ago | (#24787513)

Nah, if you're running qmail, just put a .qmail-something in your homedir containing the address to forward it to:

Say you have:
someguy@example.com

~/.qmail-fart:
someguy@example.com

Makes this address forward to someguy@example.com:
someguy-fart@example.com

Re:superparanoid? regexp (1)

g0at (135364) | more than 5 years ago | (#24788307)

The same example and process apply for the Courier suite (a much better alternative to qmail ;)), though substitute ".courier" for ".qmail".

-b

Re:Solution: salt your emails (1)

lysergic.acid (845423) | more than 5 years ago | (#24788253)

that would be up to the site admin to do that, not the attacker. and i see no reason for sites like Digg or Last.fm to fuck with the e-mail address you input. if people find out that they are removing the +, then they will just lose security/privacy-conscious users.

Re:Solution: salt your emails (5, Informative)

geekgirlandrea (1148779) | more than 5 years ago | (#24787361)

Except that lots and lots of web sites fail at RFC 822 and think + isn't a valid character in an e-mail address. Usually the same sort of maldesigned horrors that make you type your e-mail address twice even though, unlike your password, you can read it as you type to make sure it's correct, or have a single free-form blank for credit card numbers and enforce some idiosyncratic rule on separators (really, is $cc =~ s/-//g; that hard?), or enforce strong passwords and then cripple them with mandatory 'security' questions that allow anyone who knows you halfway well to reset your password.

Yeah, I use them too, and if web designers were a whole lot smarter they would be a better solution to things like this, but in practice lots of web sites just refuse to accept addresses like that. I should get around to making sendmail let me use an underscore instead of a + for that purpose.

Re:Solution: salt your emails (1)

Kent Recal (714863) | more than 5 years ago | (#24788717)

or enforce strong passwords and then cripple them with mandatory 'security' questions that allow anyone who knows you halfway well to reset your password.

How about sites that want "5-10 characters, only letters and numbers please"? Those are my personal favorites.

Re:Solution: salt your emails (4, Informative)

statemachine (840641) | more than 5 years ago | (#24787421)

Giving out e-mails with "+something" is worthless for spam. The malicious spammers will just strip the "+something" from address, as both can be delivered, but the short form will be less likely filtered, and you won't know which service it was sold/stolen from.

I actually make a separate alias for each site eg. name-something@example.com. If you shorten my alias to the part before the hyphen, it won't deliver. Yes, spammers have tried.

If you're using "+something" just know that you might as well not append that onto your e-mail address, for all the good that it does, as you're giving out your primary address anyway. Cat, bag, already open.

Re:Solution: salt your emails (4, Interesting)

geekgirlandrea (1148779) | more than 5 years ago | (#24787485)

Yeah, this can happen, but I dunno that this is as big a problem as you think. Spammers just plain aren't all that bright, and they don't care very much if they miss the tiny proportion of addresses that geeks try to protect like this when there are so many totally unprotected addresses so easy to obtain. It seems like a lot of the time, when they try to harvest addresses, the harvester doesn't realize + is a valid character in an address and only gets the part after the plus sign. I bounce a lot of spam sent to addresses like slashdot@persephoneslair.org and usenet@persephoneslair.org.

Re:Solution: salt your emails (2, Interesting)

statemachine (840641) | more than 5 years ago | (#24787843)

And the few times a harvester is correctly written? What then? That's the address that gets spread around. Obscurity doesn't work on the Internet. Just don't post it at all.

But you seem fine with it because you're also posting your personal domain name here, which links to your name and your photo, along with a street address and phone number (which I hope are only P.O. box and a voicemail-only phone service). You're a hell of a lot more comfortable with it than I am. (At least I hope you knew that all that info was very publicly available.)

Re:Solution: salt your emails (3, Interesting)

cduffy (652) | more than 5 years ago | (#24788123)

Obscurity doesn't work on the Internet.

So why bother?

Someone who was serious could get into public records and get my address anyhow (owning a house generates lots of public records). Someone who isn't serious presumably doesn't pose a threat. I think the worst thing that's actually likely to happen is 4chan-style harassment, and (1) it's not particularly likely, as I don't hang around those types enough for them to care about me, and (2) if it did happen, countermeasures are certainly available. And, again, (3) if anyone were serious enough about it, they could find all the relevant information through other channels anyhow.

Being nymous online is a Good Thing -- it means people I know IRL can recognize me (I've run into ex-coworkers and old friends I didn't think I'd see again) and it gives me a chance to build a reputation that follows me into Real Life (so potential employers find plenty to recommend me when googling my name). Further, it acts counter to the tendency for anonymous communication to degrade into... well, you're on slashdot; you know exactly what I'm talking about. :)

Re:Solution: salt your emails (1)

statemachine (840641) | more than 5 years ago | (#24788269)

(2) if it did happen, countermeasures are certainly available

No, they're not. Not in the way that you think.

1) Police are very limited in understanding and action with harassment crimes.
2) Retaliating will likely get *you* into trouble, rather than the initial tard.
3) Even if you do get a civil judgement, these people likely have nothing to lose. Therefore, you lose.
4) Sending them to jail just makes them more pissed off. Then re-visit #3.

In public forums like this, there are a lot of crazies on both sides of any argument. It's best to limit your exposure, unless you don't mind inviting trouble.

Re:Solution: salt your emails (1)

cduffy (652) | more than 5 years ago | (#24788571)

No, they're not. Not in the way that you think.

Your guesses regarding what I think are inaccurate: my idea of a fun weekend is updating the rules for my asterisk server used to filter phone spam.

To be sure, I don't particularly want to deal with cleaning up my credit report after some asshat decided to steal my identity in return for asking him to clean up his language in a public IRC channel... but hey, them's the risks with being out on the Internet these days, and (as before) I don't interact with those people enough to be a particularly likely target. (Also, my wife is a legal geek; as such, we're better prepared for effective self-representation than most, making getting that worthless civil judgment an easier process than it would be otherwise).

If we get physical vandalism... well, that depends on the time and circumstances. Malicious mischief after dark is a shooting offense here, though, making it riskier to attempt and thus less likely -- and we have dogs who tend to be defensive of their property and its owners, and adult family members with work schedules that rotate such that at least one person is home at almost all times (and able to respond if the dogs indicate trouble); as such I'm not exceptionally worried on that account.

Re:Solution: salt your emails (1)

statemachine (840641) | more than 5 years ago | (#24788759)

Well, see, that's what you're comfortable with. ;) I prefer to be happy, which, as part of my definition, excludes all the crap you have to go through to protect yourself. Sure, what I do isn't perfect, but it's yet another several steps and guesses for someone to get to the point where I need to do what you're talking about. Why make it easy?

Re:Solution: salt your emails (2, Interesting)

cduffy (652) | more than 5 years ago | (#24788919)

Hey -- we didn't arrange our schedules that way on purpose; it just happened as a happy accident. Likewise, I mess with Asterisk first and foremost because I think it's fun, and only secondarily because I dislike phone spam. (We did decide to do the large-dog thing as a security measure, but that was for late-night walks outside, not protection of the household proper -- and any weaponry we may have usable for home defense would have been purchased primary for recreational hunting; that said, I don't disclose the presence or lack of such online). I don't put myself through a whole bunch of hassle because I'm paranoid about security, and I'd probably still decide to be as easily identifiable online as I am had things not worked out that way, on account of the benefits I gave earlier (ability to translate online reputation-building into real-life interactions, which I really do think is a serious and compelling advantage)... that said, when it comes down to defending my decision, the set of happy accidents comes in handy.

I agree with you that paranoia is contrary to happiness -- that's part of why I'm comfortable with having my identity online; if I had to live in a mental state such that I believed people as a whole to be an irresponsible set (or such irresponsible people to be numerous enough to be worth thinking about), that mode of thought would, in and of itself, make me less happy.

Re:Solution: salt your emails (0)

Anonymous Coward | more than 5 years ago | (#24789901)

I might also not get STDs from having unsafe sex, doesn't mean I take that risk

Re:Solution: salt your emails (4, Insightful)

daeg (828071) | more than 5 years ago | (#24788661)

Spammers aren't bright? So spam filtering is easy, right?

One (partial) solution is to have large providers provide alternate domains that you can register throw-away addresses. For instance, under Google Account settings, you might have the option to generate an address from cephelo@gmail.com and assign d785jd47fj@southeast.gmail.com and allow you to record a note that you intend to use d785jd47fj@southeast.gmail.com as your Amazon.com user ID.

As time progresses, Gmail can show you stats that, for example, 100% of e-mail on d785jd47fj@southeast.gmail.com is spam - "Do you want to delete this account?" and poof - the spam stops. Now that address automatically becomes a honey pot.

Re:Solution: salt your emails (3, Informative)

mcrbids (148650) | more than 5 years ago | (#24790215)

Let's see... Large email provider, throwaway addresses, access until you don't want it anymore...

You mean, kinda like Mailinator [slashdot.org] ??

There are others, Mailinator is the easiest.

Re:Solution: salt your emails (1)

houghi (78078) | more than 5 years ago | (#24791263)

I use a 'trow away address' that can be spammed all they want. I use it to subscribe to sites and then I just look what the link is to activate it and sometimes also use it to re-send something. houghi.spam@gmail.com is what I use.

Some sites demand a new email address, as the old one must start paying. For those I make a new alias on my domain and as soon as I get the info, remove the alias again.

I did use the website.com@example.org and I noticed that it was way too much work to keep track of what to keep and what to delete, so I opted for what I do above.

I still get about 5 spam mails per day and this most likely because some other people have clicked on 'send this to a friend' button. Whenever I see such a button, I send it to my spam gmail and then copy the URL and send THAT to my friends.

So it is not always up to you to give out your email address.

Re:Solution: salt your emails (1)

wondershit (1231886) | more than 5 years ago | (#24791085)

Yahoo Mail has this for years now. You register a "base token" and can append another word to create a new email address. The delimiter is the "-" sign so there should be no problem with most web forms. This "base token" is independent of the email address the mails are actually sent to so there is no way (known to me) to get the real email address out of the throw away address.

So for example the real address is foo@yahoo.com and the token is bar you may start registering addresses like
  • bar-slashdot@yahoo.com
  • bar-pornmag@yahoo.com
  • ...

and drop them whenever you feel like an address isn't needed anymore. I don't really understand why this feature isn't widely recognized by the public. There is no flaw I have heard from.

Re:Solution: salt your emails (0)

Anonymous Coward | more than 5 years ago | (#24788633)

Um, you could do the same thing with the '+' system. Default label of spam, any legit address requires something to be after the plus sign...

Re:Solution: salt your emails (1)

statemachine (840641) | more than 5 years ago | (#24788785)

Um, you could do the same thing with the '+' system.

Not without modifying your MTA.

Re:Solution: salt your emails (1)

DanielLC (1346013) | more than 5 years ago | (#24789075)

Then just have people email you as +notspam, and give your email to websites without it. Of course, those websites' emails will be marked as spam, which takes away the point of giving it to them anyway. I guess this would be for stuff where you only need to get the email once.

Anyway, this doesn't matter for what the parent is saying, because if you salt your email with +akjdsflej, then the spambots will actually have to guess that. You can't just take that part out of a hash.

Re:Solution: salt your emails (1)

statemachine (840641) | more than 5 years ago | (#24789561)

Then just have people email you as +notspam, and give your email to websites without it. Of course, those websites' emails will be marked as spam, which takes away the point of giving it to them anyway.

I believe you're talking about merely filtering rather than rejection at the MTA. With my method, I don't have to modify my MTA, or add to a spam filter. Setting up another alias is not a hassle. If the alias gets spammed, I drop it, and if necessary, make a new one.

As for salting, I was indirectly saying that one wouldn't need to care about it if one used my method. But, this method only works if you control your domain's MTA like I do. If you're using Gmail, and using the "+" system, you're mistakenly trusting that the person who sends you e-mail will keep the suffix. Spammers will try both, anyway. More importantly, you can't simply shut off that "+" extension without shutting off your primary.

Re:Solution: salt your emails (1)

Z00L00K (682162) | more than 5 years ago | (#24790753)

Just consider that email addresses are a public affair.

Sometimes you want a new email address for each service you register to and by that be able to track mail harvesters if you feel like that.

The easiest way is to have a junk email address that you already get spam on when you register at various sites and then let the junk filter take care of the worst.

And expect spammers to use a lot of various techniques to circumvent obfuscation. It's all about pattern matching - and adding a lot of standard names like 'john' when flooding a site.

Re:Solution: salt your emails (1)

gwbennett (988163) | more than 5 years ago | (#24790899)

I just go one step further and make my email
slashdot.org@mydomain.com or
borders.com@mydomain.com or
amazon.com@mydomain.com

Then just have a catch all email box. If one alias starts getting junk mail I just create it as an alias to "junk@mydomain.com"

All of this hosted by mail.mydomain.com goes to google hosted services.

And it's not the domain in my slashdot info :)

Re:Solution: salt your emails (0)

Anonymous Coward | more than 5 years ago | (#24787445)

No they don't. Append != Prepend [wiktionary.org] .

Re:Solution: salt your emails (2, Informative)

aj50 (789101) | more than 5 years ago | (#24787511)

Except that some web forms (and some mail servers) won't accept an email address with a '+' in it.

We use these types of addresses at work to organise replies to tickets and some people's mail set-ups really screw things up.

Re:Solution: salt your emails (0)

Anonymous Coward | more than 5 years ago | (#24788495)

Google apps + your domain + catch all email

you can use slashdot@yourdomain.com or digg@yourdomain.com for registering on slashdot and digg

Re:Solution: salt your emails (1)

hardburn (141468) | more than 5 years ago | (#24789681)

I used to do something similar on my personal mail server. What happened was that a few poorly-administered email lists had my raw address in that form in the public archives. So now my address ended up on spammer lists three multiple times, and I'd get the same spam on three "different" addresses at the same time.

All I Know (-1, Redundant)

Anonymous Coward | more than 5 years ago | (#24786857)

All I know is I want to pound some fucking cunt!

Redundant? (-1, Offtopic)

commodoresloat (172735) | more than 5 years ago | (#24787065)

I didn't see this information in any earlier post; surely there is a better mod for this message? Then again, it might have been in the article; of course, I didn't read that.

Re:All I Know (-1, Flamebait)

Anonymous Coward | more than 5 years ago | (#24787073)

The common African nigger(Niggerus Vulgaris) is a humanoid species which is known for its gorilla-like build and its distinctive languages and aromas.

They were integrated into American society in the late 1950's/early 1960's and have since evolved into a complex, symbiotic existence with the more evolved homo sapiens species. Blacks do, however, posess attributes which may be deemed as beneficial; and these include superhuman build. Famed football coach Jimmy the Greek once famously noted that,

"...blacks were bred for strength and speed from slave days, that if blacks took over coaching positions, there would be nothing left for whites, and that blacks have a physical advantage over whites because of their thigh size."

They are known also for their larger-than-average penis size and bellicose demeanor which ensure their survival and beat out their competition.

This is all too evident as shown by the high incidence of other species' females increasingly leaving their own color and choosing male mates belonging to the niggerus vulgaris species because of the genetic advantages of having mixed-race offspring.

Niggerus vulgaris species' distinctive vocalition may sometimes mimic that of American English; for example, the rhyming "Fo-Sho" is an indicator of agreement but also showcases niggerus vulgaris' tendency to speak in rhyme whenever possible. A good example of the aforementioned phenomenon is the most recent all-niggerus Pizza Hut commercial, which depicts a family of niggerus calling and responding a collaborative poem in preparation of the feast. Their diet includes a wide variety of fruits(watermelon), vegetables(fried cabbage and collard greens), meat(fried chicken, chitterlings), and grains.

Re:All I Know (-1, Offtopic)

Anonymous Coward | more than 5 years ago | (#24787251)

You could try McCauly Kulkin. He's a real cunt.

What does MicroID actually do for the user? (1)

Butisol (994224) | more than 5 years ago | (#24786945)

I've read up on it, but I don't understand how it benefits the user, vulnerability aside.

Re:What does MicroID actually do for the user? (4, Informative)

Fred Ferrigno (122319) | more than 5 years ago | (#24787301)

I read up on it and I'm still confused, but I think this is the idea:

1. You set up an account at website Alpha.
2. You have a publicly-viewable profile page at Alpha. On the page is your MicroID.
3. You set up an account at website Beta.
4. You tell Beta about your Alpha profile page.
5. Beta verifies that your Alpha profile page is really yours by checking the MicroID.

Beta can't really do anything with your Alpha page except link to it. I guess the point would be to prevent people who aren't you from linking to your Alpha page on their Beta pages. That way, other people can be sure that the same person owns both accounts.

The attack mentioned in the article doesn't compromise the proper use of the MicroID, since Beta is assumed to have verified that you own your email address and you wouldn't link to a profile page claiming to be yours that wasn't. All it does is make it possible for spammers to harvest your email.

Re:What does MicroID actually do for the user? (0)

Anonymous Coward | more than 5 years ago | (#24789705)

It has nothing to do with Beta. Using the MicroID published by Alpha, anyone can find out the email address of you. In this case, no argument like "the attack mentioned in the article doesn't compromise the proper use of the MicroID" makes sense. The attack is really easy to mount, and really gives away your email address.

Similarly, "all it does is make it possible for spammers to harvest your email" seems like it's nothing important, even though it is. I changed my email when I started getting lots of spam, even though I used it only when registering to "trusted" sites which will "not" sell my email. Suddenly, they are selling it (when they use this MicroID)!

Re:What does MicroID actually do for the user? (1)

Fred Ferrigno (122319) | more than 5 years ago | (#24790189)

I'm not sure you read the post I was responding to. Butisol specifically asked "how it benefits the user, vulnerability aside." The only reason I mentioned the vulnerability at all was to note that it does not prevent you from reaping the benefit of MicroID.

Okay... (1)

TubeSteak (669689) | more than 5 years ago | (#24787011)

To find out valid e-mails, couldn't a spammer just send out an e-mail blast to username@top5emaildomains.com and throw away all the bounces?

You wouldn't need a hash of any sort to do that kind of trivial attack and it isn't like the serious spammers are lacking in bandwidth or resources.

Re:Okay... (0)

Anonymous Coward | more than 5 years ago | (#24787047)

You mean the bounces the spammer doesn't get because they set the from as someone else? Yeah, I doubt spammers really care what's valid and what's not at this point.

Re:Okay... (1)

chromatic (9471) | more than 5 years ago | (#24787109)

They already do. Hiding your email address in the fervent misbelief that spammers care if they have a thousand misses to one hit is security theater.

Re:Okay... (1)

Klaus_1250 (987230) | more than 5 years ago | (#24787349)

Do they still do that? I know from a distant past they tried it with smaller providers too, but haven't seen them for a long time. As far as I can tell, spammers do still use malware which harvests/sniffs email-address directly from peoples computers.

Re:Okay... (2, Informative)

WuphonsReach (684551) | more than 5 years ago | (#24787403)

Do they still do that? I know from a distant past they tried it with smaller providers too, but haven't seen them for a long time. As far as I can tell, spammers do still use malware which harvests/sniffs email-address directly from peoples computers.

This is a definite tactic. I see it all the time on a mail server that I administer. From the results, there are definitely spammers that monitor user's e-mail, address book, or other sources of e-mail addresses on their computer. (Basically, on a brand new e-mail address, the user started getting spam within a few hours of contacting someone else.)

But we still see dictionary attacks on our mail server, so that's a popular tactic too.

Re:Okay... (1)

TheNarrator (200498) | more than 5 years ago | (#24787281)

I do my own mail forwarding for a small domain that I own. There are about 20 valid email addresses at that domain. For the last year at least I have had a botnet harassing my mail server trying every conceivable random email address at my domain. I tried blocking by ip and iptables got so huge (10000+ ips) that it just about crashed my machine. I finally implemented gray listing so my machine just tells the botnet to buzz off and doesn't store any data but it's still an on-going problem. This whole botnet thing is like some surreal science fiction movie.

last I checked... (1)

Digitus1337 (671442) | more than 5 years ago | (#24787051)

Slashdot uses an e-mail scheme like that. Yeah, there it is, right there ^^^.

They already have your email address (5, Insightful)

RevDigger (4288) | more than 5 years ago | (#24787075)

This concern that you may have your email address *discovered* by spammers because you post it on a web page is so 5-years-ago. They already have your email address, and they probably didn't get it by scraping web pages.

When you have sent a couple emails out with a given address, you can figure that at least one of them will to sit around in someone's Outlook mailstore for the next couple years. (Someone you know uses Windows!) When that person's computer gets infected with spam gang malware (as they all do), they have your address.

Once of them has it, they probably all have it.

Re:They already have your email address (2, Insightful)

John Hasler (414242) | more than 5 years ago | (#24787161)

> Once of them has it, they probably all have it.

But they don't know that it is yours. They can spam you with it but they can't use it for anything else.

Re:They already have your email address (3, Insightful)

oldspewey (1303305) | more than 5 years ago | (#24788263)

They can spam you with it but they can't use it for anything else

Actually, in addition to spamming you, they can use your email address in the from and reply-to field for their next spam run.


Ask me how I know.

Re:They already have your email address (1)

hellwig (1325869) | more than 5 years ago | (#24790179)

Do you get hundreds or thousands of rejected emails a day too? I wish I could remember sending out all those advertisements for V1@GR4, or wishing people happiness in lyrical, non-sensical prose without actually trying to sell them anything.

On a serious note, how many of those rejected emails are really from email servers with admins too stupid to not respond to spam, and how many are made to look like responses in the odd hope I really did forget I sent that email, and proceed to click on all the links contained therein?

Re:They already have your email address (1)

RevDigger (4288) | more than 5 years ago | (#24789857)

It may evolve to the point that these characters will want to invest the effort in really carefully targeting their marks. I have heard it called, "spear phishing," but I have never actually seen it.

If they really wanted to do that, I would think they'd start by harvesting info from the million zombie pcs they root. I *have* seen a worm that eavesdropped on FTP to steal login info, and tag sites with malware, but that is about all I have seen in the wild.

Most of the spam/phish gang action I see, seems to be very big nets, cast very wide.

Again, that may change over time.

Re:They already have your email address (1)

Tubal-Cain (1289912) | more than 5 years ago | (#24787487)

When you have sent a couple emails out with a given address, you can figure that at least one of them will to sit around in someone's Outlook mailstore for the next couple years. (Someone you know uses Windows!)

They may use Windows, but most use of Outlook I've seen are limited to work.

Re:They already have your email address (1)

bendodge (998616) | more than 5 years ago | (#24787565)

Ok, Outlook Express. They both use a large glob files to store everything.

Re:They already have your email address (1)

Tubal-Cain (1289912) | more than 5 years ago | (#24788997)

Most people seem to use webmail.

Re:They already have your email address (2, Interesting)

coryking (104614) | more than 5 years ago | (#24790169)

The spammer (or actually, botnet owner who wrote a spam program) has already figured that out by putting a shim inbetween you and your network card. They just sniff your traffic for anything that looks interesting. In fact, I wouldn't be suprised at all that the botnet software will "turn on" when you use hit up gmail.com and can screen scrape the page while you check your email. I would even bet that it can update its screen scraping rules from some kind of distributed network.

Somebody in this thread said spammers are dumb. That might have been the case five years ago but it is not the case now. The "spam industry" has really evolved to the "botnet industry". These botnet people are smart, smart people. Almost as smart as the P2P people in terms of getting around "damage". Shame they couldn't apply their skill and talent to doing something positive for our society though.

Re:They already have your email address (2, Insightful)

cce (24686) | more than 5 years ago | (#24787597)

I'd argue that the added value of a spammer getting an email address connected to your online "identity" -- your user profile, recently-played Last.fm songs, favorite Digg articles, etc -- makes getting your email from a MicroID a little more valuable than the ordinary harvested email address. Plus, they don't have to bother confirming the address to see if it's still active (Digg already did).

Re:They already have your email address (1)

eh2o (471262) | more than 5 years ago | (#24787715)

Yes!! Not only is it pointless to try to hide, the modern spam filter (e.g., gmail) is at least 99% effective. I put my email in plaintext and even in mailto: links all over the place and I have no serious problem with spam.

Writing junk like foo [at] bar [dot] com simply wastes time time of your colleagues and friends, who now have to rewrite your address by hand, and confuses the non-techies.

*Gasp* Wrong! (1)

SeinJunkie (751833) | more than 5 years ago | (#24788653)

Writing junk like foo [at] bar [dot] com simply wastes time time of your colleagues and friends, who now have to rewrite your address by hand, and confuses the non-techies.

How dare you!? The hours I spend every week crafting clever rewrites of my email address is precisely that which keeps the spammers on their toes. How else do you think Gmail capable of filtering any spam mails out? I'm keeping their volume down. It's not just some stupid security superstition, either: it really works! And way better than whatever algorithm they're training over in Mountain View.

From,
seinjunkie@gmail.com [mailto]

It's not a secret: jeffrey@goldmark.org (2, Interesting)

Charles Dodgeson (248492) | more than 5 years ago | (#24788415)

I fully agree with the parent. The idea of keeping an email address that you actually use private is several orders of magnitude sillier than thinking your credit card number and social security number hasn't been stolen a dozen times already.

But there is one place I won't "publish" my email address (jeffrey@goldmark.org), and that is in the From line of a Usenet posting. Reply-to is fine, and there absolutely no problem in the body of messages, but tests have shown that putting something in the From line of a Usenet posting will give you a very noticeable increase in spam.

Re:They already have your email address (1)

Phroggy (441) | more than 5 years ago | (#24788441)

They're also still scraping e-mail addresses off the web. And no, just because one spammer has your address does NOT mean that all spammers have it: spammer #1 is not going to give your address to spammer #2 without compensation, so unless spammer #2 buys a collection of addresses from spammer #1 (they were going for about $500 for a database on CD-ROM last time I checked), or spammer #2 discovers your e-mail address independently, then no, spammer #2 doesn't have your address.

Re:They already have your email address (0)

Anonymous Coward | more than 5 years ago | (#24788871)

And yet you've still altered your email on Slashdot ;)

Re:They already have your email address (1)

steevc (54110) | more than 5 years ago | (#24791081)

Spammers got my main email ages ago and seem to have hacked a few forums for one-off addresses I used there too. So I don't worry too much about giving out my email address. The spam is mostly filtered, so I don't have to see it.

I'm not sure exactly where they got my address from. It could have been on a keyserver. Searching for my address finds lots of hits on those. Much easier than trying to extract it from a MicroID. Those were potentially useful for proving identity.

That said, spammers, identity thieves and other low-lifes have conspired to make the internet less useful than it might have been since we cannot share as much information as we might want to. I'm still wary of sharing some details on social sites and in my FOAF file. Others seem less bothered about this or perhaps just don't realise the risks.

The internet could have been a universal phone/address/email directory, but too many people would abuse that.

A better solution? (1)

donkeyoverlord (688535) | more than 5 years ago | (#24787165)

What would be a better solution that is as easy to implement?

Re:A better solution? (3, Insightful)

Firehed (942385) | more than 5 years ago | (#24787515)

Use gmail. I'll get a thousand or so spams a month, but I've had maybe four make it to my inbox in the past three years.

It obviously doesn't eliminate the problem of spam, but in theory if it didn't make it to anyone's inbox, idiots would stop acting on it and suddenly spam wouldn't be profitable and would fizzle away.

Re:A better solution? (1)

Americium (1343605) | more than 5 years ago | (#24788721)

But I wanna update my penis!

And that's only available in my spam folder!

I do thoroughly enjoy theory tho, as do most /. readers.... it's a shame most people are stuck in reality... hahahaha....sucks for them, as they require it to.

Re:A better solution? (1)

shentino (1139071) | more than 5 years ago | (#24791393)

Actually, spammers don't get their profits from you actually receiving it. That's actually one of the last things on their minds.

Spammers, through the usage of botnets and other means, take business from shady dealers who are trying to sell the crap in the first place.

The spammer profits by sending the emails on behalf of Huge Penis Incorporated, and they really couldn't give a damn whether anyone actually buys the stuff. It's pure profit margin for the spammer no matter how many people actually bother to act.

Of course, they have to keep up appearances. Emails not getting through makes their reputation as spammers go down...so they have to do something just to make themselves look marketable to companies who push the stuff. But as far as actual ROI, that's really not the spammer's concern. They don't have to reach you, they just have to make their clients think they are.

The company that sells the stuff loses becuase nobody gives a crap about their stuff. The poor hapless souls with stuffed inbuxes lose because their email has been overrun. The only winner is the spammer who was paid money to send the junk mail, as well as any botnet operators he rents from.

Seriously, it's a spammer. Do you think anyone who is nasty enough to flood our inboxes and associate with botnet operators would actually give a crap about how profitable he is making his "clients" by running ads for them?

Don't use Gravatar (1)

wtfispcloadletter (1303253) | more than 5 years ago | (#24787241)

This is exactly the reason I don't use Gravatar. They even tell everyone they are morons right here:
http://en.gravatar.com/site/implement/url [gravatar.com]

I didn't know anything about them except that someone in a forum was describing how you could have the same avatar in compatible forums that you participate in. The second I read that your hashed email address was part of the URL I turned around and never looked back knowing full well that if someone wanted to, they could eventually get my email address.

Re:Don't use Gravatar (1)

SanityInAnarchy (655584) | more than 5 years ago | (#24788727)

The second I read that your hashed email address was part of the URL I turned around and never looked back knowing full well that if someone wanted to, they could eventually get my email address.

Erm, WTF?

I don't like Gravatar either, as it's a centralized service, and one which frequently goes down.

But you're afraid that, given a hash, someone can find your email address? Do you understand how hashing works?

Re:Don't use Gravatar (1, Informative)

Anonymous Coward | more than 5 years ago | (#24788895)

Uh... Do you realise what the article you're commenting on is about?

Re:Don't use Gravatar (1)

SanityInAnarchy (655584) | more than 5 years ago | (#24789957)

I guess I'll have to actually read it, but I'm still not getting the premise.

How is a hash of my email address in any way valuable personal data that I shouldn't expose? I mean, yeah, it tells someone my email address, provided they already know my email address. What's the point?

Methods (1)

YoungFelon (674090) | more than 5 years ago | (#24787297)

cce, how did you confirm a successful application of your method? If each site used a unique 'secret key' to salt the hash, would it prevent breakability? I run a small site that uses globally recognized avatars, which are implemented with hashed email addresses. Thanks for doing this study!

Obscuring email addresses is fairly useless anyway (1)

mellon (7048) | more than 5 years ago | (#24787311)

The bottom line is that unless you don't have any online presence, your email address is going to leak, and it's going to wind up on spammer's lists. If you want to avoid getting spam, some other solution is called for.

even the spec admits it is retarded (2, Informative)

hdon (1104251) | more than 5 years ago | (#24787345)

I wrote about this earlier this year. [socsurveys.org] My conclusion, more or less, was to carefully read the specification, which Iâ(TM)ll excerpt here:

By itself, a MicroID has no inherent meaning, since it is simply a string created from two URIs. Any entity can generate a MicroID even if it has not verified the identity of the resources associated with one or both URIs. Furthermore, a MicroID is easily copied by an entity that did not generate it. Finally, a MicroID is not digitally signed by the entity that generated it and therefore cannot be cryptographically associated with the generating entity.

Mod this up! + Windows should have crypto applet (0)

Anonymous Coward | more than 5 years ago | (#24790687)

This is the most important post in the whole comment thread. That with publishing your MicroID you publish your e-mail address is one thing, but that the MicroID isn't actually an ID in any sense of the word is quite another. Why is Windows' cryptography tool exposed as an API, but didn't Microsoft ship an applet with it that uses it? For example, they could have added PGP support to Notepad and the e-mail and messenger applets with relative ease, but but they didn't do so. Why? And that of course was the reason why MicroID didn't ask users to sign it, because most users don't have a clue on how to do it. And those that do know often refuse to install GnuPG because then they 'need to install something'. Seriously, Windows should have more accessible crypto support.

Email. (1)

changa (197280) | more than 5 years ago | (#24787389)

People still use E-Mail?

Re:Email. (1)

Tubal-Cain (1289912) | more than 5 years ago | (#24787499)

Only old ones in South Korea.

Gravatar? (1)

ilovesymbian (1341639) | more than 5 years ago | (#24787495)

Huh, I guess I won't be using gravatar anymore :(

considered harmful considered harmful (1, Funny)

Anonymous Coward | more than 5 years ago | (#24787521)

Oh the terrible price we paid for salvation from goto...

Flawed study? (2, Insightful)

dmuir (964412) | more than 5 years ago | (#24787583)

What's the difference between attacking the MicroID to collect email addresses, and running a dictionary attack on email servers using people's usernames?

Re:Flawed study? (3, Informative)

QuantumG (50515) | more than 5 years ago | (#24787745)

Offline attacks are better because they:

1. can't be monitored
2. can't be blocked
3. are not limited by bandwidth
4. can be sped up by throwing more hardware at them

This is basically why salting was added to the unix password file. And that failed.. so /etc/shadow was introduced. Revealing hashes is just unnecessary, so don't do it.

Re:Flawed study? (1)

cce (24686) | more than 5 years ago | (#24787813)

I address this question in the paper [brown.edu] and on the tiny FAQ here [brown.edu] . Basically, DHAs require a spammer to interactively query an email server and blindly guess popular names: here, the server can throttle or block access to these requesters, and the success rate is very low.

With MicroID, the tokens are meant for public use, and thus can accessed with a simple HTTP GET. Cracking them yields much higher success rates (25% from Digg) than DHAs, as well as a "verified" user email, & links to that user's associated content (e.g., favorite Last.fm songs for ringtone spam, favorite Digg articles).

Re:Flawed study? (1)

WuphonsReach (684551) | more than 5 years ago | (#24789377)

here, the server can throttle or block access to these requesters, and the success rate is very low.

You make a possibly faulty assumption here.

Just like spam runs can be spread across hundreds of thousands of machines, so can dictionary attacks. Which makes it a lot harder to block or throttle access to random IPs.

Re:Flawed study? (1)

Toveling (834894) | more than 5 years ago | (#24787945)

Because this way, you can do it locally. Let your computer do a few hundred thousand hashes a second, instead of trying to send email to each possible address. Additionally, by attacking the microID, you get extra info about the person (maybe even firstname, lastname, etc).

Why don't you want people to have your address? (1)

EWAdams (953502) | more than 5 years ago | (#24787963)

Personally, I can't get clients unless they know how to get in touch with me.

And don't moan about spam. My E-mail address is widely published and maybe one or two messages a week gets through the filters.

Re:Why don't you want people to have your address? (0)

Anonymous Coward | more than 5 years ago | (#24788133)

So what about the processor time required to filter out spam? Is it infinite? Or free?

fuCK! (-1, Flamebait)

Anonymous Coward | more than 5 years ago | (#24788657)

leg1timIse doing

Bad news for Gravatar (1)

porneL (674499) | more than 5 years ago | (#24788693)

I guess Gravatar.com will now have to ecourage proxying of avatars via sites' web servers.

Is this attack really that signficant? (0)

Anonymous Coward | more than 5 years ago | (#24788811)

It sounds like what the author did is take each username, and then try hashing @gmail.com, @yahoo.com, etc. If that's the case, a spammer could just skip the hashing trouble and try emailing those same addresses directly.

Why is this a big deal? (4, Insightful)

Ed Avis (5917) | more than 5 years ago | (#24790763)

You are worried because someone, if they really wanted to send you some mail, could go to the trouble of doing a CPU-intensive search against some hash shown on a website and find out that ultimate, embarassing secret: your *email address*??

What gives? Email addresses are designed to be public. If you don't want people you do not know to be able to contact you, then you are free to drop all mail from unrecognized addresses. If you want to set up some kind of secret knowledge that people must have in order to contact you, then ask them to put a particular word in the subject line when first sending you a message. Either of these does not rely on keeping the address secret, which just isn't likely to happen.

The only thing more broken than trying to keep an email address secret is trying to make a 'private' web page by keeping the URI secret. Again, the system is designed so that the address itself is not sensitive, but other information such as a password or PGP key can be.

Actually, what it reminds me of most is the crazy situation in the US where a basically public identifier, the social security number, is abused as some kind of secret token. Hence all the fuss made when it is possible to find out someone's SSN. The answer is not to add more and more baroque means to stop the SSN from leaking out: one breach, and it's no longer a secret.

I understand the desire to stop spam address harvesters, but really, there are hundreds of web sites which display email addresses with only light obfuscation, enough to stop a harvester bot but not a determined human being (or someone determined enough to use an OCR engine). The kind of hashing talked about here is way more difficult to undo than that. If you are even more paranoid, you need to revisit your assumptions of what is public and what is secret.

Load More Comments
Slashdot Login

Need an Account?

Forgot your password?
or Connect with...

Don't worry, we never post anything without your permission.

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>