WORM_SILLY.FK
Symantec: W32.SillyFDC ; Microsoft: Worm:Win32/Autorun.PI ; Kaspersky: Trojan.Win32.Antavmu.iu
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Worm
Destructiveness: No
Encrypted: Yes
In the wild: Yes
OVERVIEW
Copies itself in all available physical drives, Propagates via removable drives
This worm arrives by connecting affected removable drives to a system. It may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.
It bypasses the Windows firewall. This allows the malware to perform its intended routine without being detected by an installed firewall.
It drops copies of itself in all removable and physical drives found in the system. It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.
TECHNICAL DETAILS
131,072 bytes
PE
Yes
14 Dec 2010
Arrival Details
This worm arrives by connecting affected removable drives to a system.
It may be dropped by other malware.
It may be unknowingly downloaded by a user while visiting malicious websites.
Installation
This worm drops the following copies of itself into the affected system:
- %Windows%\{random name}.exe
- %System%\{random name}.exe
- %System%\{random name}.exe
- %Windows%\system\{random name}.exe
- %Windows%\inf\{random name}.exe
- %Windows%\Config\{random name}.exe
- %Program Files%\Common Files\{random name}.exe
(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %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.. %Program Files% is the default Program Files folder, usually C:\Program Files.)
Autostart Technique
This worm adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
RSetting = %Windows%\inf\{random name}.exe
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
UserTools = %Program Files%\common files\{random name}.exe
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
CheckS = %Windows%\config\{random name}.exe
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
DeviceSys = %System%\{random name}.exe
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
tDefault = %System%\{random name}.exe
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Settings = %Windows%\{random name}.exe
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
SystemT = %Windows%\system\{random name}.exe
Other System Modifications
This worm modifies the following registry entries to disable the Windows Firewall settings:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile
EnableFirewall = 0
(Note: The default value data of the said registry entry is 1.)
Propagation
This worm drops copies of itself in all removable and physical drives found in the system.
It drops the following copies of itself in all physical and removable drives:
- arquivos.exe
- program.exe
It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.
The said .INF file contains the following strings:
[AUTORUN]
open=program.exe e
Shellexecute=program.exe e
Shell\Auto\Command=program.exe e
Shell=Auto
Other Details
This worm does the following:
- Drops copies of itself and an AUTORUN.INF file in mapped drives.
SOLUTION
8.900
7.701.00
14 Dec 2010
12/14/2010 12:00:00 AM
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
Identify and terminate files detected as WORM_SILLY.FK
- If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
- If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.
Step 3
Delete this registry value
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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- RSetting = %Windows%\inf\{random name}.exe
- RSetting = %Windows%\inf\{random name}.exe
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- UserTools = %Program Files%\common files\{random name}.exe
- UserTools = %Program Files%\common files\{random name}.exe
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- CheckS = %Windows%\config\{random name}.exe
- CheckS = %Windows%\config\{random name}.exe
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- DeviceSys = %System%\{random name}.exe
- DeviceSys = %System%\{random name}.exe
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- tDefault = %System%\{random name}.exe
- tDefault = %System%\{random name}.exe
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- Settings = %Windows%\{random name}.exe
- Settings = %Windows%\{random name}.exe
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- SystemT = %Windows%\system\{random name}.exe
- SystemT = %Windows%\system\{random name}.exe
Step 4
Restore this modified registry value
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\SharedAccess\Parameters\FirewallPolicy\StandardProfile
- From: EnableFirewall = 0
To: EnableFirewall = 1
- From: EnableFirewall = 0
Step 5
Search and delete AUTORUN.INF files created by WORM_SILLY.FK that contain these strings
Step 6
Scan your computer with your Trend Micro product to delete files detected as WORM_SILLY.FK. 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.
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