Threat behavior
TrojanDownloader:Win32/Vildo.P takes the following actions when it runs:
- If there is no copy of itself in %windir% (the Windows installation folder):
- Creates a copy of itself in %windir%. The copy has the same name as the original Trojan downloader file. The icon for the new file resembles the default icon for PDF files.
- Adds the following entry in the registry to cause itself to run automatically each time the current user logs on:
Creates value: winldr
with data: %windir%\<Trojan downloader file name>
in registry subkey: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run - Runs the copy of the downloader file that is in %windir%.
- Creates a batch file named a.bat in the same folder as the original Trojan downloader file. When it runs, the batch file deletes the original Trojan downloader file.
- Injects itself into the Windows explorer.exe process in memory. Running in the context of explorer.exe allows the Trojan to conceal itself and bypass local software firewall policies. The injected code downloads programs from URLs that are specified in the Trojan downloader file. The downloader may save any of the downloaded programs locally as a file named dllsys.dll in the Windows system folder. TrojanDownloader:Win32/Vildo.P then runs the downloaded programs without notifying the user.
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
Click Start, and click Control Panel.
Click Network and Internet Connections. If you do not see Network and Internet Connections, click Switch to Category View.
Click Change Windows Firewall Settings.
Select On.
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
Click Start, and click Control Panel.
Click System.
Click Automatic Updates.
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/athome/security/downloads/default.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.
