Microsoft is really a hard target for malware. Maybe it was because many are against its monopolistic approach. MS had just released Windows Vista (the much-delayed Longhorn renamed), and a file infector has just been discovered that specifically targets it.

This file infector affects only Microsoft .NET Framework 2.0 which is included in Vista Beta 1. It overwrites .EXE files with its code. This action renders such files useless.

The impact of this file infector is very low – Vista is not in wide use, and as such, it is not an imminent threat to general users. It made the news because it is the first to attack a just recently released beta version of a future MS operating system.

Trend Micro’s description for this infector is here. Symantec has its description here.

Note: The only question that remains unanswered at the moment: Microsoft .NET 2.0 Beta is already available for other MS operating systems, are they also affected by this file infector? If so, the risk becomes larger, specially for developers who use the 2.0 Framework and SDK.

Update: It affects all Windows systems, as long as .NET Framework 2.0 is installed.