Malicious Software Encyclopedia: Win32/Bobax
Published:
November 8, 2005
Win32/Bobax is a family of mass-mailing network worms that targets certain versions of Microsoft Windows. The worm can spread by sending a copy of itself as an attachment to e-mail addresses gathered from an infected computer. It can also spread by exploiting several Windows vulnerabilities. The worm can download and run malicious files from Web sites, and can also open a backdoor to give attackers access to use the infected computer.
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Threat Overview
| Class/type | Worm - Mass Mailer
Worm - Network
|
| Discovered | August 16, 2005 |
| Circulating | Yes |
| Affected operating systems | Windows 2000
Windows XP
Windows Server 2003
Windows 98
|
| Affected software |
Not specified
|
| Infection rating | Low |
| Recovery difficulty | Moderate |
| Damage rating | Medium |
| Transmission rating | Low |
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):
Sophos:
W32/BobaxSymantec:
W32.Bobax
Learn more about the
Microsoft Virus Information Alliance.
Related Security Bulletins
The following Microsoft Security bulletins are related to this issue:
MS03-026 - Buffer Overrun In RPC Interface Could Allow Code Execution (823980)MS03-039 - Buffer Overrun In RPCSS Service Could Allow Code Execution (824146)MS04-011 - Security Update for Microsoft Windows (835732)MS05-039 - Vulnerability in Plug and Play Could Allow Remote Code Execution and Elevation of Privilege (899588)Technical Analysis
Win32/Bobax may take actions such as the following:
- Create a copy of itself in <system folder> or %windir%. The file name is random for most Win32/Bobax variants.
- Create values in the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Software\Microsoft\Windows\CurrentVersion\Run
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
These changes cause the worm to run each time Windows starts and whenever a user logs on. They also cause the worm to run as a service in the current session and each time Windows starts, so the worm is always running regardless of whether any user is logged on. - Open and monitor a random TCP port to enable attackers to use the infected computer as a proxy.
- Download and run files from various Web sites.
- Drop a .dll file, inject the .dll code into the explorer.exe process space, and run the code. The .dll file that is dropped is a Win32/Bobax variant.
- Modify registry keys to disable Windows firewall security.
- Modify the Windows hosts file, <system folder>\drivers\etc\hosts, to block access to certain computer security and shopping Web sites.
Win32/Bobax may spread in the following ways:
- By sending a copy of itself as an attachment to e-mail addresses that it gathers from various locations.
- By exploiting various Windows vulnerabilities. The worm creates a thread to scan random IP addresses on TCP port 135 or 445 in order to connect to remote computers. If a connection is established, the worm may copy itself to the remote computer by exploiting one of these Windows vulnerabilities:
- The Microsoft Windows Plug-and-Play buffer overflow vulnerability (Microsoft Security Bulletin MS05-039)
- The RPC DCOM vulnerability (Microsoft Security Bulletins MS03-039 and MS03-026)
- The LSASS vulnerability (Microsoft Security Bulletin MS04-011)
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. If you don't have antivirus software installed, you can get it from one of several companies. For more information, see http://www.microsoft.com/athome/security/downloads/default.mspx
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.
How to Tell If Your Computer Is Infected
There may be no readily apparent indications that your computer is infected by Win32/Bobax. Your computer may be infected by this worm if you notice any of the following symptoms:
- Excessive, unexpected network traffic on TCP port 135 or 445.
Unexpected loss of Windows firewall functionality.
Unexpected changes to the Windows hosts file.
Inability to access certain computer security and shopping Web sites.
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 |
|---|
| Exploits Vulnerability | Exploits several windows vulnerabilities to spread to random IP addresses. |
| Infected Files | Drops a .dll file and injects it into the explorer.exe process space. |
| Mass Mailer | Sends a copy of itself as an attachment to e-mail addresses on the infected computer. |
Payload Information
| Payload type | Trigger | Description |
|---|
| Creates files | Execution | - Copies itself to the system folder or %windir%.
- Drops a .dll file to inject the .dll code into the explorer.exe process space.
|
| Compromises Security | Execution | Modifies registry keys to disable Windows firewall security. Modifies the Windows hosts file to block access to computer security and shopping Web sites. Opens and monitors a TCP port to enable attackers to use the computer as a proxy. Downloads and runs files from Web sites. Injects .dll code into the explorer.exe process space and runs the code.
|
Affected Ports
| Protocol | Port number |
|---|
| TCP | 445 |
| TCP | 135 |
