Malicious Software Encyclopedia: Win32/Sober

Published: December 16, 2005

Win32/Sober is a family of mass-mailing worms that targets certain versions of Microsoft Windows. The worm sends itself as an attachment to e-mail addresses that it finds in files on the infected computer. The worm is activated when a user opens the attachment.

Severity

What the levels mean

Glossary Terms

Click the term to get the definition from our Security Glossary.

•	Trojan horse
•	virus
•	worm

Threat Overview

Class/type	Worm - Mass Mailer
Discovered	February 21, 2005
Circulating	Yes
Affected operating systems	Windows 95 Windows 2000 Windows XP Windows Server 2003
Affected software	Not specified
Infection rating	Low
Recovery difficulty	Easy
Damage rating	Low
Transmission rating	Medium

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Technical Analysis

When a variant of Win32/Sober runs, it takes the following actions:

Creates one or more files at <system folder>\<random>.exe and runs them.

Creates a registry value with data: <full path>
in registry keys:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
This causes the worm to run automatically whenever Windows starts.

Retrieves e-mail addresses that it finds in files on the infected computer, avoiding addresses that contain certain strings.
Creates the file <system folder>\<random>, where it saves those e-mail addresses.

Sends itself as an attachment to the e-mail addresses. The e-mail has a subject line and message body that is in English or German. The e-mail attachment may have one of the following extensions:
.bat
.exe
.pif
.src
.zip

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How to Prevent Infection

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 unknown attachments.

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, and click Network Connections. If you do not see Network and Internet Connections, click Switch to Category View.
Highlight a connection that you want to help protect, and click Change settings of this connection.
Click Advanced, and select Protect my computer and network by limiting or preventing access to this computer from the Internet.
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 Microsoft 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 Performance and Maintenance. If you do not see Performance and Maintenance, click Switch to Category View.
Click System.
Click Automatic Updates, and select Keep my computer up to date.
Select a setting. Microsoft recommends selecting Automatically download the updates, and install them on the schedule that I specify and setting a regular update time.
If you choose to have Automatic Updates notify you in step 5, you will see a notification balloon when new downloads are available to install. Click the notification balloon to review and install updates.

Use up-to-date antivirus software

Most antivirus software can detect and prevent infection by known malicious software. You should always run antivirus software on your computer that is updated with the latest signature files to automatically help protect you from infection.

Use caution with unknown attachments

Use caution before opening unknown e-mail or IM attachments, even if you know the sender. If you cannot confirm with the sender that a message is valid and that an attachment is safe, delete the message immediately, and run up-to-date antivirus software to check your computer for viruses.

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