Gmail CAPTCHA cracked

Posted by   Virus Bulletin on   Feb 26, 2008

Twenty per cent success rate sufficient to create thousands of spam accounts.

Gmail has become the latest free webmail service to have its CAPTCHAs cracked by spammers.

Following the recent news of the Yahoo Mail and Windows Live Mail CAPTCHAs having been cracked, the news of Gmail's CAPTCHA being surpassed will come as little surprise.

Gmail, known as Google Mail in some countries, is the free webmail service offered by Google. Before being able to set up a new Gmail account, users are required to solve a CAPTCHA - which was believed to be very hard to crack - thus preventing automated registration of accounts.

However, using the combined forces of two hosts, spammers have managed to crack the Gmail CAPTCHAs with a success rate of one in five. As the registration attempts are carried out by bots in a botnet, this is a suffienctly high success rate to allow the attackers to create a large number of free accounts from which to send spam.

Researchers at security company Websense, who first discovered the attack, believe that it is being carried out by the same group behind the cracking of Windows Live Mail CAPTCHAs earlier this month.

Like both Windows Live Mail and Yahoo Mail, Gmail is a valuable resource for spammers - providing free access to powerful mailing resources, and with its broad popularity and large legitimate user base it provides a domain address that is unlikely to be blocked by spam filters - thus stepping up the challenge for spam- and malware-fighters.

More details are at Websense here and at The Register here.

Posted on 26 February 2008 by Virus Bulletin

twitter.png
fb.png
linkedin.png
googleplus.png
reddit.png

 

Latest posts:

Mostly blocked, but still good enough: Necurs sending pump-and-dump spam

The Necurs botnet has started sending pump-and-dump spam. Almost all of these emails are blocked by spam filters, yet the stock price still increased.

Why the SHA-1 collision means you should stop using the algorithm

Realistically speaking, if your software or system uses the SHA-1 hashing algorithm, it is unlikely that it will be exploited in the foreseeable future. But it is also extremely difficult to be certain that your system won't be the exception.

VB2017 Call for Papers: frequently asked questions

The call for papers for VB2017, which takes place 4 to 6 October in Madrid, Spain, is currently open. We're always on the look out for new speakers and new content, so to help anyone who's unfamiliar with the VB conference, we've prepared a list of…

Throwback Thursday: Michelangelo - Graffiti Not Art

This week marked the 25th anniversary of the trigger date of the infamous Michelangelo virus. In January 1992, VB published an analysis of the boot sector virus that captured the imagination of the press and kicked up a media storm.

How are you defending your network? Come and tell us at VB2017!

Is it your job to defend your company’s network? Are you defending a government’s systems? Do you help secure the devices used by activists operating in less open societies? Do you work with abuse victims targeted by spyware? Share your experiences…