The company released its largest group of security patches in nearly a year, posting 12 security bulletins encompassing 19 vulnerabilities, 14 of which it marked "Critical." Among them is a vulnerability that one security vendor claims will likely lead to the biggest, baddest worm since mid-2003.

Microsoft Tuesday released its largest group of security patches in nearly a year as it posted 12 security bulletins encompassing 19 vulnerabilities, 14 of which it marked "Critical," its highest warning. Among them is a vulnerability that will likely lead to the biggest, baddest worm since mid-2003, said Mike Murray, the director of research at vulnerability management vendor nCircle. "There's a clear 'winner' here," said Murray. " MS05-011 fixes a vulnerability in SMB [Server Message Block], which is running on every version of Microsoft's operating systems that a corporation might be using. And it's exploitable remotely, so it doesn't rely on an e-mail or getting someone to a Web site. All the attacker has to do is send a properly-formatted packet and he'll break in.