Threat behavior
Win32/Clodpuntor is a trojan that sends spam e-mail.
Installation
When executed, it copies itself to %windows%\taskmon.exe from where it is then executed. It also modifies the registry to execute this copy at each Windows start:
Adds value: taskmon
With data: "%windows%\taskmon.exe"
To subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
It also creates the mutex {v4085-4ccc49fb-e033-4a64-8adf-e648a658f798} to ensure that multiple copies of the trojan do not run simultaneously.
Payload
Firewall Modification
Win32/Clodpuntor adds itself (%windows%\taskmon.exe) as an 'allowed program' to the Windows firewall by invoking "netsh".
Contacts Remote Hosts/Downloads Files
Win32/Clodpuntor contacts a remote host to determine if there is a newer version of itself available, and performs an update if required.
Win32/Clodpuntor attempts to determine if it is able to perform outbound connection on TCP port 25
During this process, various DNS lookups are initiated to hosts such as:
hotmail.com
yahoo.com
smtp.yahoo.com
relay.yahoo.com
mxs.yahoo.com
mx1.yahoo.com
mx.yahoo.com
mail.yahoo.com
mail1.yahoo.com
gate.yahoo.com
Sends Spam E-mail
Win32/Clodpuntor also contacts 208.101.56.102 in order to retrieve the data it uses to construct spam e-mails. This includes the content of the e-mail itself as well as a list of e-mail addresses to send to.
Analysis by Scott Molenkamp
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.
To turn on the Windows Firewall in Windows Vista
Click Start, and click Control Panel.
Click Security.
Click Turn Windows Firewall on or off.
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/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.
