This time it was Microsoft Live Hotmail’s CAPTCHA that has fallen victim to hackers. CAPTCHA, which stands for Completely Automated Public Turing test to tell Computers and Humans Apart, is often used by Webmail services to prevent spammers from using bots to sign up for multiple accounts.

Microsoft has reworked its CAPTCHA in the past to thwart cracking attempts by hackers, but as research from Websense shows, these latest efforts have still come up short. 

In a detailed analysis, Websense researcher Sumeet Prasad noted that spammers have increased the sophistication of their anti-CAPTCHA efforts in the latest attack. While in the past anti-CAPTCHA operations used automation that utilized straightforward, command and control instructions from a template, the latest attack uses automation with encrypted communication between spammer bot servers and compromised machines, the researcher blogged.