Three of the seven patches Microsoft released on Tuesday earn the dread rating of critical.
Updates involving flaws in handling streaming media by Microsoft DirectX, bugs in Windows Media Format Runtime, and multiple vulnerabilities in IE all pose a severe risk.
In all three cases the vulnerabilities addressed by the update create a possible means for miscreants to smuggle malware onto, or otherwise attack, vulnerable Windows boxes. But the IE update deserves special attention since hackers are actively exploiting the bug to attack vulnerable machines, the SANS Institute's Internet Storm Centre warns.
The remaining four "important" updates address bugs including a brace of bugs in Windows Vista and a security bug in DRM software from Macrovision that comes bundled with Windows. Macrovision issued a patch to address flaws in its SafeDisk utility in November, which is just as well because the bug has become the target of various attacks by crackers.