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When entering your email address publicly, a practice is to replace . with text dot and @ with text at. I assume that the reasoning is that this way automatic email-collector robots won't match your address so easily. I still see updated websites using this.

However, this practice is not very hard to workaround with a program, and it has been around since more than a decade (as of 2013). Anyone in the business of collecting emails had quite enough time to update all their robots to handle this. Are there still robots that doesn't handle this? Why?

Are there any reasons remaining today to use this kind of mangling?

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1  
Munging is necessary to write URLs in YouTube comments. "www.ninelivesrec.dev" becomes "vvv ninelivesrecs dev". –  Iain Elder Nov 6 '13 at 23:07
    
If your primary language is not English but for example Latvian, then dot in Latvian is punkts. I don't think that crawlers understood Latvian :) But this works only for small languages. Also if in email address contains numbers, you can write it: email_two_ at gmail punkts com (remove __ and two is 2) –  Guntis Nov 12 '13 at 7:15

4 Answers 4

up vote 52 down vote accepted

To understand this, we must understand how crawlers find the email. While steering away from the technicals, the basic idea is this (today's algorithms are, of course, smarter than that):

  1. Find @ in the page.
  2. Is there a dot within 255 characters after the @?
  3. Grab what's behind the @ until you reach a space or the beginning of the line.
  4. Grab the . and what's behind it until you reach the @.
  5. Grab what's after the . until your reach the end of the line or a space.

Now, an easy countermeasure would be to replace the @ with at and the . with dot. The most intuitive counter-countermeasure would be to teach the crawler that at is actually @. Well, it's not that simple. Take the following text:

We climbed into the attic and found a dotted piece of wood. Please email us: adnan at gmail dot com.

Now let's run our new crawler on it. First it will find the at in attic, then it will find the dot in dotted. The resulting email would be the@ticandfounda.ted, then it will find the second email adnan@gmail.com. Then spammers started teaching crawlers about finding certain domains, ignoring spaces, taking spaces into account, considering certain domain names, etc.

Then we started using images, spammers used OCR. We started using JavaScript tricks, inserting comments, URL-encide, etc. and always the spammers found a way to get around them. It's a race.

Having that said, the most basic techniques usually give good enough results (apparently, in some place in the world, that link is NSFW. Personally, I disagree), and the more obfuscate, the better results you get.

enter image description here

So, to directly answer your question: Is using 'dot' and 'at' in email addresses in public text still useful? Yes, I think so, at least to some degree. But this solution has been around long enough for us to assume that most crawlers have already found a way around it.

My advice? Either use some fancy advanced munger, or simply use images.

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I can't imagine people who collect email addresses are unaware that addresses that are obfuscated are more likely to belong to people who are less likely to answer spam. –  Random832 Nov 6 '13 at 18:32
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People who harvest email addresses are selling them in bulk to spammers. Quantity means everything to profits. Quality is determined by a Boolean test: did an SMTP server not reject email to this address? There is no concern for "is this person likely to respond?" –  John Deters Nov 6 '13 at 18:55
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To protect your bike from thieves, you don’t need an unbreakable bike lock; you just need it to be stronger than most of the other cyclists’ locks. The graph you give shows that the same principle holds here. –  PLL Nov 6 '13 at 21:03
    
@PLL Precisely! –  Adnan Nov 6 '13 at 21:05
    
That's a useful study. Someone should do a similar study, adding in images. –  LarsH Nov 6 '13 at 22:39

To my humble opinion, email obfuscation (of any sort) is one of the worse ideas ever invented.

The foremost concern for any user interface, web based or any other, is convenience and safety of its users. Spam bots are not users, thus they are not worth any consideration or effort.

The logic goes as following:

  1. E-mail obfuscation is a nuisance for legitimate users. Rather than simply clicking the mailto link, user will be forced to manually type in e-mail address into their mail address prompt.

    1.a. Even this by itself may deter the user from contacting the intended address - they will go elsewhere to simply avoid tedious interaction.

    1.b. The chance to enter erroneous but similar address in the process and thus send the possibly important mail to some typo-scamming mailbox is very high.

  2. Most legitimate e-mail addresses in existence are already known to spammers. Every mail box I've encountered to date (and this is a rather large number of mailboxes) was receiving some volume of spam on a regular basis. This is why all contemporary mail servers and clients come with spam filter integration, which, in most cases, is very efficient.

In short, just use plain and normal "mailto:" links and don't annoy your users unnecessarily.

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Oh, you can still put a normal mailto link behind the obfuscated fooÄTexampleDOTcom. Kind of defeats the purpose, but I have seen this so many times, that I must conclude a lot of the people using ATs and DOTs don't even know why (or have no understanding of crawlers at all). –  linac Nov 7 '13 at 9:14
    
I didn't get any true spam at my personal addresses until just a few months ago. Probably some person or company leaked my emails then. It's certainly not true that every legitimate address gets spam. –  Mehrdad Aug 16 at 10:42

I have never understood the paradigm since its conception. We are simply depriving spam battling software the necessary data. As mentioned before, adding "at" "dot" to the parser is trivial too.

I would actually urge otherwise. Let the hell loose. Use your email and use any email for that matter. I even wrote a bot 10 years ago or so, where it produced infinite random emails page by page. If a crawler hit it, it would forever crawl non-existent emails.

We should not reduce the emails spam bots have to process. We should increase the number so in turn resource requirements, hence the cost of running a spammer would get higher and spam becomes less feasible economically.

We should take quality of spam filters into account when choosing a mail service so they get economical benefit while spam keeps hurting.

We have many instruments in place today which did not exist a decade ago. DKIM, SPF, reverese-PTR, blacklists and whatnot. Spam is getting less and less attractive. We should push it forward. Let it handle the load not ourselves.

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Interesting idea. And it doesn't have to be either/or; it could be both/and: obfuscate your real email address, and dump chaff on the spam bots. –  LarsH Nov 6 '13 at 22:42
    
....so you're the reason I get spam with multiple "To" addresses, Izkata / Izkaya / Izkaa / Izkaat....? –  Izkata Nov 7 '13 at 3:57
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Flawless logic! Let's all unlock our bikes together, this way it'll be such a burden on bike thieves to steal all those bikes, which will force them to stop stealing bikes. Now if we apply it on the Internet spam, I'm sure it'll work. I mean, let's look at other advertisement methods, the more the bigger the audience, the more they want to stop advertising. Just look at Google Ads, radio ads, TV commercials, physical spam mail, etc. –  Adnan Nov 7 '13 at 8:39
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@Adnan if only one bike among a million is sold (hence the clicks to ads), it's something to consider for thieves yes. because they would be employing a million people just to sell one bike. –  ssg Nov 7 '13 at 9:09
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@adnan No, You're surrounding your bike with a bunch of two wheeled paper mache bikes and making your real bike look like a heap of spare parts. The bike thieves come and grab all the paper mache and leave yours alone! I think I like this idea. –  TecBrat Nov 7 '13 at 14:07

"Is using 'dot' and 'at' in email addresses in public text still useful?"

Good though responses have been, I rather doubt that it's ever been useful, and would expect email harvesters to have been scanning for that obfuscation even before people were naively using it (I certainly would have if I were in that game).

Our own tests have also shown that it doesn't take long before spam arrives on an email address that hasn't been disclosed on the web at all, with it likely being harvested from recipients address books and mail folders on a compromised machine; obfuscating an email address is in general at best only going to delay the inevitable and not actually prevent it.

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