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Win32/Tilcun


Win32/Tilcun is a family of trojans that steals online game passwords and sends this captured data to remote sites.
 


What to do now

Manual removal is not recommended for this threat. To detect and remove this threat and other malicious software that may have been installed, run a full-system scan with an up-to-date antivirus product such as the Microsoft Safety Scanner (http://go.microsoft.com/fwlink/?LinkId=212742). For more information, see http://www.microsoft.com/protect/computer/viruses/vista.mspx.

Threat behavior

Win32/Tilcun is a family of trojans that steals online game passwords and sends this captured data to remote sites.
Installation
When executed, Trojan:Win32/Tilcun drops a DLL to the System folder using a variant-specific filename (for example, one variant drops the file <system folder>\wrqszl.dll). It then drops another file, <system folder>\winsys.reg and uses it to modify the registry to load the DLL at each Windows start:
Adds value:  “0”
With data: "{<clsid>}"
To subkey: HKLM\SOFTWARE\MICROSOFT\WINDOWS\CURRENTVERSION\EXPLORER\SHELLEXECUTEHOOKS
 
Add value:  <dll filename>
With data “(default)”
To subkey: HKLM\SOFTWARE\Classes\CLSID\<clsid>\INPROCSERVER32
where <clsid> is a hex string for the CLSID and <dll filename> is the filename of the dropped DLL mentioned above.
 
For example:
Adds value:  "(default)"
With data: "<system folder>\wrqszl.dll"
To subkey: HKLM\SOFTWARE\Classes\CLSID\{F99DEFDD-200B-4410-B572-E90883D527D2}\INPROCSERVER32
 
Note - <system folder> refers to a variable location that is determined by the malware by querying the Operating System. The default installation location for the System folder for Windows 2000 and NT is C:\Winnt\System32; and for XP and Vista is C:\Windows\System32.
Payload
Steals Online Game Passwords
Win32/Tilcun sets up hooks in order to capture login information for popular online games. It then sends the captured data to a remote site.
 
Analysis by Chun Feng

Symptoms

System Changes
The following system changes may indicate the presence of Win32/Tilcun:
  • Presence of the following file:
    <system folder>\winsys.reg

Prevention

Take the following steps to help prevent infection on your system:
  • Enable a firewall on your computer.
  • Get the latest computer updates.
  • Use up-to-date antivirus software.
  • Use caution with attachments and file transfers.
Enable a firewall on your computer
Use a third-party firewall product or turn on the Microsoft Windows XP Internet Connection Firewall.
To turn on the Internet Connection Firewall in Windows XP
  1. Click Start, and click Control Panel.
  2. Click Network and Internet Connections. If you do not see Network and Internet Connections, click Switch to Category View.
  3. Click Change Windows Firewall Settings.
  4. Select On.
  5. Click OK.
To turn on the Windows Firewall in Windows Vista
  1. Click Start, and click Control Panel.
  2. Click Security.
  3. Click Turn Windows Firewall on or off.
  4. Select On.
  5. Click OK.
Get the latest computer updates
Updates help protect your computer from viruses, worms, and other threats as they are discovered. You can use the Automatic Updates feature in Windows XP to automatically download future Microsoft security updates while your computer is on and connected to the Internet.
To turn on Automatic Updates in Windows XP
  1. Click Start, and click Control Panel
  2. Click System.
  3. Click Automatic Updates.
  4. Select a setting. Microsoft recommends selecting Automatic. If you do not choose Automatic, but you choose to be notified when updates are ready, a notification balloon appears when new downloads are available to install. Click the notification balloon to review and install the updates.
Use up-to-date antivirus software
Most antivirus software can detect and prevent infection by known malicious software. To help protect you from infection, you should always run antivirus software that is updated with the latest signature files. Antivirus software is available from several sources. For more information, see http://www.microsoft.com/protect/computer/viruses/vista.mspx.
Use caution with attachments and file transfers
Exercise caution with e-mail and attachments received from unknown sources, or received unexpectedly from known sources.  Use extreme caution when accepting file transfers from known or unknown sources.

Alert level: Severe
This entry was first published on: Jun 10, 2008
This entry was updated on: Apr 17, 2011

This threat is also detected as:
No known aliases