FYI from one of my newsletters…and I apologise for the the length of the post!
Threat Level: Serious
Threat Name: W32/Sasser.worm.a
Threat Type: Virus/ Internet Worm
NOTE: Systems which are regularly updated with the latest updates from Microsoft are not vulnerable to this Worm. It is critical that you keep your Windows system updated by checking http://windowsupdate.microsoft.com/ and keeping your Anti-Virus program updated several times per week. If you don’t have Anti-Virus software get AVAST (free for home use) at http://www.avast.com/ .
This self-executing worm spreads by exploiting a Microsoft Windows vulnerability [MS04-011 vulnerability (CAN-2003-0533)]
The worm spreads with the file name: avserve.exe . Unlike many recent worms, this virus does not spread via email. No user intervention is required to become infected or propagate the virus further. The worm works by instructing vulnerable systems to download and execute the viral code.
If you think that you may be infected with this threat, and are unsure how to check your system, you may download the Stinger tool to scan your system and remove the virus if present.
Note: Infected systems should install the Microsoft update to be protected from the exploit used by this worm. See:
http://www.microsoft.com/technet/security/bulletin/MS04-011.mspx
In order to secure you system from potential new variants of this worm which may be introduced in the near future make sure you have your Windows updated with the latest security patches and fixes from http://windowsupdate.microsoft.com/
How It Spread and Works:
This worm spreads by exploiting a recent Microsoft vulnerability, spreading from machine to machine with no user intervention required.
This 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. This FTP script instructs the target victim to download and execute the worm (with the filename #_up.exe as aforementioned) from the infected host. The infected host accepts this FTP traffic on TCP port 5554.
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 destination port is TCP 445
The virus copies itself to the Windows directory as avserve.exe and creates a registry run key to load itself at startup
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows
CurrentVersion\Run “avserve.exe” = C:\WINDOWS\avserve.exe
As the worm scans random ip addresses it listens on successive TCP ports starting at 1068. It also acts as an FTP server on TCP port 5554, and creates a remote shell on TCP port 9996.
A file named win.log is created on the root of the C: drive. This file contains the IP address of the localhost.
Copies of the worm are created in the Windows System directory as #_up.exe.
Examples
c:\WINDOWS\system32\11583_up.exe
c:\WINDOWS\system32\16913_up.exe
c:\WINDOWS\system32\29739_up.exe
A side-effect of the worm is for LSASS.EXE to crash, by default such system will reboot after the crash occurs.
If you think you may be infected, download the McAfee Stinger tool to remove it:
Manual Removal Instructions
To remove this virus manually, follow these steps:
Reboot the system into Safe Mode (hit the F8 key as soon as the Starting Windows text is displayed, choose Safe Mode.
Delete the file AVSERVE.EXE from your WINDOWS directory (typically c:\windows or c:\winnt)
Edit the registry
Delete the “avserve” value from
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft
Windows\CurrentVersion\Run
Reboot the system into Default Mode
I did have my system scanned and was not infected
also, got another patch from Windows today…
HTH,
cojo