Malicious Software Encyclopedia: Win32/Bugbear
Published:
November 15, 2005
Win32/Bugbear is a family of mass-mailing network worms that targets computers running certain versions of Microsoft Windows. The worm spreads through e-mail and network shares. It can also spread by infecting files in folders of file-sharing applications. The worm drops a Trojan to gather data from the infected computer and opens a port on the computer to receive commands from attackers.
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Threat Overview
| Class/type | Virus - File
Worm - Mass Mailer
Worm - Network
|
| Discovered | September 30, 2002 |
| Circulating | Yes |
| Affected operating systems | Windows NT 4.0
Windows 95
Windows 2000
Windows XP
|
| Affected software | Internet Explorer 4.0
Internet Explorer 4.01
Internet Explorer 5
Internet Explorer 5.5
Outlook 2000
Outlook 2002
Outlook 98
Outlook Express 5.01
Outlook Express 5.5
Outlook Express 6.0
|
| Infection rating | Medium |
| 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):
McAfee:
W32/Bugbear.gen@MM Symantec:
W32.Bugbear@mm
Learn more about the
Microsoft Virus Information Alliance.
Related Security Bulletins
The following Microsoft Security bulletins are related to this issue:
MS01-020 - Incorrect MIME Header Can Cause IE to Execute E-mail AttachmentMS01-027 - Flaws in Web Server Certificate Validation Could Enable SpoofingTechnical Analysis
Win32/Bugbear copies itself to locations such as the Windows startup folder and Windows system folder. It disables security-related programs and other applications and modifies the registry in order to run automatically each time Windows starts.
The worm can drop a Trojan .dll file that records and sends keystrokes to attackers. The worm also opens a TCP port as a backdoor to receive commands from attackers, return information, and connect to a Web server. An attacker can use the backdoor to perform operations such as running or deleting files, terminating processes, gathering passwords, and collecting keystrokes that the .dll file captures. The worm can distribute the collected data through e-mail, HTTP, or the backdoor.
The worm spreads by sending a copy of itself as an attachment to e-mail addresses found on the computer. The attachment can have a double extension, such as .txt.exe. The worm runs when the user opens the attachment. If Microsoft Security Bulletin MS01-020 or MS01-027 is not installed on the computer, the worm runs when the user only previews or opens the e-mail that contains the attachment.
The worm can also spread by copying itself to the Startup folder of writeable administrator network shares. The worm then runs automatically on the remote computer each time Windows starts. The worm can disrupt shared network resources, such as causing a printer to print many pages of useless data.
Some Win32/Bugbear variants are polymorphic file infectors. The worm targets frequently used applications such as regedit.exe and notepad.exe, appending its code to the file. Some variants create worm copies in other locations, such as in folders of certain file-sharing applications. The worm copy uses the name and extension of an existing file in the folder and appends an .exe extension. For example, if there is a file named abc.jpg in the folder, the worm can create a copy of itself there named abc.jpg.exe.
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.
Use strong passwords.
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. 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.
Use strong passwords
A strong password has at least eight characters and includes a combination of letters, numbers, and symbols. It is easy for you to remember, but difficult for others to guess. Weak passwords include any words in the dictionary, names, dates, consecutive letters or numbers, common words with symbol substitutions (for example, p@ssw0rd), and so on.
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 are no readily apparent indications that your computer is infected with Win32/Bugbear.
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 |
|---|
| Mass Mailer | Sends a copy of itself as an attachment to e-mail addresses found on the computer. |
| Social Engineering | Runs when user opens the attachment. If MS01-020 or MS01-027 is not installed, the worm runs when the user simply previews or opens the e-mail containing the attachment. The attachment can have a double extension. The worm can append a second extension to the name of executable files that it infects. |
| Exploits Vulnerability | Exploits the Windows vulnerability patched by MS01-020 or MS01-027. |
| Network Shares | Copies itself to writeable administrator shares on other computers. |
| Infected Files | Infects executable files by appending worm code to the file. |
Payload Information
| Payload type | Trigger | Description |
|---|
| Creates files | Execution | Copies itself to folders such as the system folder, program files folder, and start up folder on writeable administrator shares on other computers. Can drop a Trojan .dll keylogger file.
|
| Sends e-mails | Execution | Sends a copy of itself as an attachment to e-mail addresses found on the computer. |
| Deletes files | Execution | Can delete files in response to commands from attackers. |
| Release information | Execution | Gathers information such as keystrokes to distribute through e-mail, HTTP, or through a backdoor. |
Modified Registry Entries
| Changed registry entries |
|---|
| Key | |
| Value name | |
| Old value | |
| New value | |
