We recently discovered a new bootkit, i.e. a malicious program which infects the hard drive’s boot sector. Kaspersky Lab detects it as Rookit.Win32.Fisp.a. The bootkit is distributed by Trojan-Downloader.NSIS.Agent.jd. The Trojan infects the computers of users who try to download a video clip from a fake Chinese porn site.

This downloader is remarkable in that it downloads other malicious programs using a NSIS engine and stores all links in the relevant NSIS-script.

Fragment of the NSIS script for Trojan-Downloader.NSIS.Agent.jd

The dropper Rootkit.Win32.Fisp.a is among the files downloaded by the Trojan-downloader. This malicious program infects the hard drive’s boot sector. More specifically, it saves the old MBR to the third sector and replaces it with its own. Starting with the fourth sector, it installs an encrypted driver and the remaining code.

Fragment from the start of the hard disk infected by Rootkit.Win32.Fisp.a