W32/Sachy.worm

Upon execution of file "csrss.exe", it attempts to download the following files from the remote ftp server "[removed].fm260.com".

• yes.bat
• wmi.vbs
• smss.exe (detected as Portscan-EggDrop)

The batch file "yes.bat" runs smss.exe to scan for machines on the network with tcp port 135 open. Then wmi.vbs attempts to connect each machine found with empty administrator password, and runs the WMI remote script to download "csrss.exe" from the remote ftp server.

The worm also adds the following registry key.

• HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon "Userinit"=  C:\WINDOWS\system32\userinit.exe,C:\WINDOWS\system32\Setup\csrss.exe,

• Presence of the files and registry entries detailed above

Infect other machines on the network via the WMI remote script with a weak administrator password.

All Users:
Use current engine and DAT files for detection and removal.

Modifications made to the system Registry and/or INI files for the purposes of hooking system startup, will be successfully removed if cleaning with the recommended engine and DAT combination (or higher).

But in some particular cases, the following steps need to be taken.

Please go to the Microsoft Recovery Console and restore a clean MBR.

On Windows XP:

• Insert the Windows XP CD into the CD-ROM drive and restart the computer.
• When the "Welcome to Setup" screen appears, press R to start the Recovery Console.
• Select the Windows installation that is compromised and provide the administrator password.
• Issue 'fixmbr' command to restore the Master Boot Record
• Follow onscreen instructions.
• Reset and remove the CD from CD-ROM drive.

On Windows Vista and 7:

• Insert the Windows CD into the CD-ROM drive and restart the computer.
• Click on "Repair Your Computer".
• When the System Recovery Options dialog comes up, choose the Command Prompt.
• Issue 'bootrec /fixmbr' command to restore the Master Boot Record.
• Follow onscreen instructions.
• Reset and remove the CD from CD-ROM drive.