With the
February release of security patches Microsoft is attempting to kill what it is referring to as one of the largest botnets currently active worldwide, zombie machines infected with Win32/Srizbi. According to
Vincent Tiu, SDE II at Microsoft, the Srizbi family of malicious code contains not only trojan droppers but also rootkits, which work in tandem in order to compromise vulnerable machines and to make them part of botnets used with predilection to spread spam. As of February 10, 2009, the Microsoft Windows Malicious Software Removal Tool is capable of detecting and cleaning computers compromised by the Srizbi family of malware.