This is a virus detection. Viruses are programs that self-replicate recursively, meaning that infected systems spread the virus to other systems, which then propagate the virus further. While many viruses contain a destructive payload, it's quite common for viruses to do nothing more than spread from one system to another.
Indication of Infection
Presense of the file avserve3.exe
and registry key:
CurrentVersion\Run "avserve3.exe" = C:\WINDOWS\avserve3.exe
Methods of Infection
This worm spreads by exploiting a recent Microsoft vulnerability, spreading from machine to machine with no user intervention required.
The propagation mechanism is akin to that for previous variants:
- the worm scans random IP addresses for exploitable systems. When one is found, the worm exploits the vulnerable system, by overflowing a buffer in LSASS.EXE.
- It creates a remote shell on TCP port 9996.
- Next it creates an FTP script named cmd.ftp
on the remote host and executes it. Via the FTP script, the FTP.EXE application is used to retrieve the worm from the infected machine (port 9996) to the remote host. The worm is then executed.
- the FTP script instructs the target victim to download and execute the worm (with the filename #_up.exe as mentioned above) from the infected host.
- The infected host accepts this FTP traffic on TCP port 9996.
The worm spawns multiple threads, some of which scan the local class A subnet, others the class B subnet, and others completely random subnets. The worm scans public ranges like 10.0.0.0 and 192.168.0.0 only if they are part of the local subnet. The destination port is TCP 445.
Sasser.G (F-Secure), W32.Sasser.G (Symantec), Worm.Win32.Sasser.g (AVP)