TROJ_VILSEL.PB
VirTool:WinNT/Emold.B (Microsoft); Suspicious.SillyFDC (Symantec); Worm.Win32.Emold (v) (Sunbelt); Win32/Cryptor (AVG)
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Trojan
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It deletes itself after execution.
TECHNICAL DETAILS
Arrival Details
This Trojan 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 Trojan drops the following copies of itself into the affected system:
- %System%\logon.exe
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)
Autostart Technique
This Trojan modifies the following registry entries to ensure it automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe logon.exe"
(Note: The default value data of the said registry entry is Explorer.exe.)
Other System Modifications
This Trojan deletes the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
explorer.exe
Dropping Routine
This Trojan drops the following files:
- %User Temp%\rdl1.tmp
- %User Temp%\rdl4.tmp
- %System%\DRIVERS\asyncmac.sys
- A:\autorun.exe
(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.. %System% is the Windows system folder, which is usually C:\Windows\System32.)
Other Details
This Trojan connects to the following possibly malicious URL:
It deletes itself after execution.
This report is generated via an automated analysis system.
SOLUTION
Step 1
Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.
Step 2
Identify and delete files detected as TROJ_VILSEL.PB using either the Startup Disk or Recovery Console
Step 3
Restore these modified registry values
Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: Shell = "Explorer.exe logon.exe"
To: Shell = ""Explorer.exe""
- From: Shell = "Explorer.exe logon.exe"
Step 4
Search and delete these components
- %User Temp%\rdl1.tmp
- %User Temp%\rdl4.tmp
- %System%\DRIVERS\asyncmac.sys
- A:\autorun.exe
Step 5
Scan your computer with your Trend Micro product to delete files detected as TROJ_VILSEL.PB. 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
Restore these deleted registry keys/values from backup
*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- explorer.exe
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