Malicious Software Encyclopedia: Win32/Codbot
Published:
November 15, 2005
Win32/Codbot is a family of network worms that targets computers running certain versions of Microsoft Windows. Some variants of this family spread to network shares with weak administrator passwords. Other Win32/Codbot variants spread by exploiting one or more Windows vulnerabilities. The worm has a backdoor component that connects to an IRC server from an infected computer to receive commands from attackers.
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Threat Overview
| Class/type | Worm - Network
|
| Discovered | February 25, 2005 |
| Circulating | Yes |
| Affected operating systems | Windows NT 3.x
Windows NT 4.0
Windows 95
Windows 2000
Windows XP
Windows Server 2003
Windows ME
Windows 98
|
| 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.ToxbotKaspersky:
Backdoor.Win32.CodbotMcAfee:
W32/Sdbot.worm.genSophos:
W32/Codbot-GenSymantec:
W32.ToxbotTrend Micro:
WORM_CODBOT
Learn more about the
Microsoft Virus Information Alliance.
Related Security Bulletins
The following Microsoft Security bulletins are related to this issue:
MS02-039 - Buffer Overruns in SQL Server 2000 Resolution Service Could Enable Code Execution (Q323875)MS02-061 - Elevation of Privilege in SQL Server Web Tasks (Q316333)MS03-007 - Unchecked Buffer In Windows Component Could Cause Server Compromise (815021)MS03-026 - Buffer Overrun In RPC Interface Could Allow Code Execution (823980)MS04-011 - Security Update for Microsoft Windows (835732)Technical Analysis
Win32/Codbot copies itself to the Windows folder or Windows system folder. The worm-copy file name depends on the variant. The worm may use the file name of a legitimate program, such as regedit.exe. The worm may register itself and run as a service with a display name and description that seem legitimate, such as display name "Registry Editor" and description "Handling all user and system made register changes." Some variants modify registry entries so the worm runs automatically even when Windows starts in safe mode.
Win32/Codbot connects to a specific IRC server and channel to receive commands from attackers. This can include commands to report its status to attackers, scan for unpatched computers on the network, join and leave IRC channels, download and run files using HTTP, open a TFTP or FTP server, and retrieve system information such as IP addresses and operating system version.
The worm spreads in two ways:
By copying itself to network shares. The worm may log on to the administrator account on a network share using weak passwords until it gains share access.
By exploiting various Windows vulnerabilities to copy itself to other computers. The worm scans random IP addresses to find computers that have not been patched for certain Windows vulnerabilities. This includes vulnerabilities described in the following Microsoft Security Bulletins MS02-039, MS02-061, MS03-007, MS03-026, MS04-011. For example, after using a weak administrator password on a SQL Server 2000 host, the worm can send a packet to the SQL Server Resolution Service to exploit the MS02-039 vulnerability. This allows the worm to create a remote command shell on the SQL Server host and use the shell to copy and run the worm there.
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.
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 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/Codbot.
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 various Windows vulnerabilities. |
| Network Shares | Spreads to network shares using weak administrator passwords. |
Payload Information
| Payload type | Trigger | Description |
|---|
| Creates files | Execution | File name and location varies by variant. |
| Compromises Security | Execution | Connects to a specific IRC server and channel to receive commands from attackers. |
