WORM_PRASH.A

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It takes advantage of software vulnerabilities to propagate across networks.

Arrival Details

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This worm drops the following files:

• %System%\slsvcx.exe - also detected as WORM_PRASH.A
• %System%\tcpwalhlib.exe - also detected as WORM_PRASH.A
• %System%\drivers\tcpz-x86d.sys - detected sa HKTL_PRASH

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Autostart Technique

This worm registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\TCPZ
ImagePath = "\??\%System%\drivers\tcpz-x86d.sys"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\WalhSvc
ImagePath = "%System%\tcpwalhlib.exe"

Propagation

This worm takes advantage of the following software vulnerabilities to propagate across networks:

• DCOM RPC vulnerability using TCP port 135
• RPC Locator vulnerability using TCP port 445

Backdoor Routine

This worm connects to the following URL(s) to send and receive commands from a remote malicious user:

• net.{BLOCKED}a.com

Other Details

More information on this vulnerability can be found below:

• MS04-012
• MS08-067 Server Service Remote Execution Exploit

NOTES:
This worm also takes advantage of a vulnerability in MSSQL Server using TCP port 1433 that allows remote attackers to obtain sensitive information, alter database content and compromise SQL servers. More information on this vulnerability can be found in MS02-034.