Malicious Software Encyclopedia: Win32/Sobig
Published:
February 27, 2005
Win32/Sobig is a family of mass-mailing worms that targets computers running certain versions of Microsoft Windows. The worm sends itself to e-mail addresses that it finds on the infected computer. The worm may also spread to writeable network shares.
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Threat Overview
| Class/type | Worm - Mass Mailer
|
| Discovered | January 9, 2003 |
| Circulating | Yes |
| Affected operating systems | Windows NT 4.0
Windows 95
Windows 2000
Windows XP
Windows Server 2003
|
| Affected software |
Not specified
|
| Infection rating | Low |
| Recovery difficulty | Moderate |
| Damage rating | Medium |
| Transmission rating | Medium |
Aliases (Also Known As)
Different antivirus vendors may be using different names to refer to this malicious software. Here are some of the names currently in use by antivirus software vendors participating in the Microsoft Virus Information Alliance (VIA):
CA:
Win32.SobigF-secure:
SobigGlobal Hauri:
I-Worm.Win32.SobigMcAfee:
W32/Sobig@MM Norman:
W32/Sobig@mmPanda:
SobigSophos:
W32/SobigSymantec:
W32.Sobig@mmTrend Micro:
WORM_SOBIG
Learn more about the
Microsoft Virus Information Alliance.
Technical Analysis
When a Win32/Sobig variant runs, it copies itself to the Windows folder, and creates an entry in the following registry keys:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run, HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
These registry entries cause the worm to run automatically whenever Windows starts. The worm then attempts to spread by sending itself as an attachment to e-mail addresses that it finds on the infected computer. It also attempts to spread through writeable network shares. Some variants also download and run files from some URLs.
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.
Remove unneeded network shares.
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.
Remove unneeded network shares
Malicious software can often spread over network shares. Remove unneeded network shares that are mapped to your computer.
To remove network shares in Windows XP
On the Start menu, click My Computer.
On the Tools menu, click Disconnect Network Drives…
In the Disconnect Network Drives dialog box, click the drives to disconnect and click OK.
How to Tell If Your Computer Is Infected
There may be no readily apparent indications that your computer is infected by a variant of the Win32/Sobig family. However, your computer may be infected by this worm if you notice any of the following symptoms:
- Significant slowdowns during normal operation.
- Increased outbound SMTP traffic.
How to Recover from Infection
Automatic Recovery
To attempt to automatically remove this threat, run one of the following removal tools:
Transmission Methods
| Method | Description |
|---|
| Network Shares | Copies itself to writeable network shares. |
| Mass Mailer | Uses its own SMTP engine for mass mailing. |
Payload Information
| Payload type | Trigger | Description |
|---|
| Compromises Security | Execution | Downloads potentially malicious programs to run on the infected computer. |
| Sends e-mails | Execution | Spreads through e-mail attachments. |
Affected Ports
