Kaspersky Labs has detected a mass mailing of a new Trojan named Agent. Agent infects victim machines when users view graphics in BMP format. Agent exploits a vulnerability in MS Internet Explorer versions 5.0 and 5.5 which allows malicious code to be launched on victim machines via modified BMP files. This vulnerability is a direct result of the Windows source code leak and was first detected on February 16, 2004. Agent was mailed using spammer technology in an infected email that only contains a BMP file with a random name. The file is created especially for the Russian version of Windows 2000; the malicious code will not function on other language versions. This implies that Agent was probably created in Russia or the CIS. Should a user open the BMP file Agent immediately connects to a remote server located in the Lybian domain zone, downloading and installing a second Trojan named Throd. Throd is a classic spyware program. The Trojan first copies itself into the Windows system registry autorun keys and then awaits further commands. The 'master' can remotely execute various commands on the victim machine including copying data, collecting addresses from MS Outlook and turning the infected computer into a proxy server functioning as a platform for anonymous cyber crimes. "Throd is obviously written for spammers,' comments Eugene Kaspersky, Head of Anti-Virus Research at Kaspersky Labs, 'the Trojan harvests email addresses and creates a network of zombie machines for massive spammer attacks. Once again, we see spammers and virus-writers are working hand in hand." To date, Microsoft has not issued a patch for this vulnerability. In other words, the only protection users have is up-to-date anti-virus software. "Moreover, it is very likely that malware attacking other versions of Windows will soon appear', adds Eugene Kaspersky, 'I strongly recommend that users make sure that their antivirus software protects them from malware exploiting this particular Windows vulnerability." Kaspersky® Anti-Virus does scan the contents of BMP files and automatically detects suspicious objects attempting to penetrate via either the Internet of email. The solution neutralizes Agent automatically and our antivirus databases have been updated to detect Throd. Detailed descriptions of both Agent and Throd are available in the Kaspersky Virus Encyclopedia.