Microsoft is advising users to reinstall Windows if they happen to be unfortunate enough to get hit by a particularly vicious rootkit.
The Popureb Trojan sticks its tendrils so deep into the operating system that the best option is to
nuke from orbit return machines to their original configuration. Any files that aren't backed up will be lost in the process.
Drastic measures are needed because a new version of the malware includes a driver component designed to prevent a malicious Master Boot Record and other malicious data dropped by the Trojan from being removed.
"If your system does get infected with Popureb-E Trojan, we advise you to fix the MBR and then use a recovery CD to restore your system to a pre-infected state (as sometimes restoring a system may not restore the MBR), advises Microsoft security response staffer Chun Feng in a blog post here:
http://blogs.technet.com/b/mmpc/archive/2011/06/22/don-t-write-it-read-it-instead.aspx"To fix the MBR, we advise that you use the System Recovery Console, which supports a command called 'fixmbr'."
Microsoft doesn't say so explicitly, but applying a Master Boot Record fix before using a recovery disc is going to strip infected systems of both installed applications and associated data. In those circumstances, you'd need to use computer forensics skills to get anything back, a calamitous situation that illustrates the need to regularly back up important data.
(ElReg)