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
hackernews.png
reddit.png

 

Latest posts:

VB2021 localhost call for last-minute papers

The call for last-minute papers for VB2021 localhost is now open. Submit before 20 August to have your paper considered for one of the slots reserved for 'hot' research!

New article: Run your malicious VBA macros anywhere!

Kurt Natvig explains how he recompiled malicious VBA macro code to valid harmless Python 3.x code.

New article: Dissecting the design and vulnerabilities in AZORult C&C panels

In a new article, Aditya K Sood looks at the command-and-control (C&C) design of the AZORult malware, discussing his team's findings related to the C&C design and some security issues they identified.

VB2021 localhost call for papers: a great opportunity

VB2021 localhost presents an exciting opportunity to share your research with an even wider cross section of the IT security community around the world than usual, without having to take time out of your work schedule (or budget) to travel.

New article: Excel Formula/Macro in .xlsb?

In a follow-up to an article published last week, Kurt Natvig takes us through the analysis of a new malicious sample using the .xlsb file format.

We have placed cookies on your device in order to improve the functionality of this site, as outlined in our cookies policy. However, you may delete and block all cookies from this site and your use of the site will be unaffected. By continuing to browse this site, you are agreeing to Virus Bulletin's use of data as outlined in our privacy policy.