WORM_PRASH.A
Worm:MSIL/Prash.A (Microsoft); Trojan-Dropper.Win32.VB.ncs (Kaspersky)
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Worm
Destructiveness: No
Encrypted: Yes
In the wild: Yes
OVERVIEW
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.
TECHNICAL DETAILS
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:
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.
SOLUTION
Step 1
For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.
Step 2
Remove malware files dropped/downloaded by WORM_PRASH.A
- HKTL_PRASH
Step 3
Restart in Safe Mode
Step 4
Delete this registry key
Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
- TCPZ
- TCPZ
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
- WalhSvc
- WalhSvc
Step 5
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_PRASH.A. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.
Step 6
Download and apply these security patches Refrain from using these products until the appropriate patches have been installed. Trend Micro advises users to download critical patches upon release by vendors.
Did this description help? Tell us how we did.