Gmail CAPTCHA cracked

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