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Malicious Software Encyclopedia: Win32/Sdbot

Published: June 14, 2005

Win32/Sdbot is a family of backdoor Trojans that allows attackers to control infected computers. After a computer is infected, the Trojan connects to an internet relay chat (IRC) server and joins a channel to receive commands from attackers. These commands can instruct the Trojan to spread to other computers and can allow attackers to perform other backdoor functions, such as launching denial of service (DoS) attacks and retrieving system information from infected computers.

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Glossary Terms

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Trojan horse

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virus

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worm

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On This Page
Threat OverviewThreat Overview
Aliases (Also Known As)Aliases (Also Known As)
Related Security BulletinsRelated Security Bulletins
Technical AnalysisTechnical Analysis
How to Prevent InfectionHow to Prevent Infection
How to Tell If Your Computer Is InfectedHow to Tell If Your Computer Is Infected
How to Recover from InfectionHow to Recover from Infection
Transmission MethodsTransmission Methods

Threat Overview

Class/typeTrojan - Backdoor
DiscoveredApril 16, 2003
CirculatingYes
Affected operating systemsWindows NT 4.0
Windows 95
Windows 2000
Windows XP
Windows Server 2003
Affected software Not specified
Infection ratingMedium
Recovery difficultyModerate
Damage ratingMedium
Transmission ratingLow

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/SDBot
  • F-secure: SdBot
  • McAfee: W32/Sdbot.worm
  • Symantec: Backdoor.Sdbot
  • Trend Micro: WORM_SDBOT

    • Learn more about the Microsoft Virus Information Alliance.

    Related Security Bulletins

    The following Microsoft Security bulletins are related to this issue:

  • MS01-059 - Unchecked Buffer in Universal Plug and Play Can Lead to System Compromise
  • MS02-061 - Elevation of Privilege in SQL Server Web Tasks (Q316333)
  • MS03-001 - Unchecked Buffer in Locator Service Could Lead to Code Execution (810833)
  • MS03-007 - Unchecked Buffer In Windows Component Could Cause Server Compromise (815021)
  • MS03-026 - Buffer Overrun In RPC Interface Could Allow Code Execution (823980)
  • MS03-043 - Buffer Overrun in Messenger Service Could Allow Code Execution (828035)
  • MS03-049 - Buffer Overrun in the Workstation Service Could Allow Code Execution (828749)
  • MS04-011 - Security Update for Microsoft Windows (835732)

    • Technical Analysis

    When Win32/Sdbot runs, it copies itself to %windir% or <system folder>. In many cases, it adds a value to one or more registry keys. These changes cause the Trojan to run whenever Windows starts. Some variants also add a Windows system service to attain similar results.
     
    Win32/Sdbot connects to an internet relay chat (IRC) server and joins a channel to receive commands, which can include actions such as:
    • Scanning for unpatched computers on the network.
    • Scanning ports on the network.
    • Downloading and running remote files.
    • Monitoring network traffic.
    • Launching HTTP/HTTPD, SOCKS4, and TFTP/FTP servers.
    • Enabling or disabling DCOM protocol.
    • Retrieving computer configuration information, including Windows logon information, user account information, open shares, file system information, and network connection information.
    • Logging keystrokes.
    • Retrieving CD keys of games.
    • Capturing screens and Webcam shots.
    • Redirecting TCP traffic.
    • Uploading files through FTP.
    • Sending e-mail.
    • Manipulating processes and services.
    • Conducting denial of service (DoS) attacks.
     
    Upon receiving IRC commands, the Trojan can spread to remote computers by exploiting one or more Windows vulnerabilities. Win32/Sdbot can spread to remote computers by trying weak passwords that it draws from a fixed list. The Trojan may exploit the MS03-026 vulnerability to create a remote shell on a computer. The Trojan uses the remote shell to copy and run itself on a remote computer. The Trojan can also be instructed through IRC commands to spread through backdoor ports opened by Mydoom, Bagle, Optix, Netdevil, and other malicious software families.
     
    Some variants of the Trojan terminate security-related products. Later variants of the Trojan can install a kernel-mode rootkit driver, which hides the Trojan process from Task Manager and other process-viewer applications.

    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 strong passwords.

    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
    1. Click Start, and click Control Panel.
    2. Click Network and Internet Connections, and click Network Connections. If you do not see Network and Internet Connections, click Switch to Category View.
    3. Highlight a connection that you want to help protect, and click Change settings of this connection.
    4. Click Advanced, and select Protect my computer and network by limiting or preventing access to this computer from the Internet.
    5. 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
    1. Click Start, and click Control Panel. 
    2. Click Performance and Maintenance. If you do not see Performance and Maintenance, click Switch to Category View.
    3. Click System.
    4. Click Automatic Updates, and select Keep my computer up to date.
    5. 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.
    6. 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.

    How to Tell If Your Computer Is Infected

    Your computer may be infected with a Win32/Sdbot variant if you experience any of the following symptoms:
    • The operating system shuts down after displaying a dialog box that resembles the following:
      System Shutdown
    • Your computer displays an LSA Shell error report dialog box that resembles the following:
    • Your computer restarts without user interaction. In this case, you may see a system shutdown dialog box that resembles the following:

    How to Recover from Infection

    Automatic Recovery
    To attempt to automatically remove this threat, run one of the following removal tools:

    Transmission Methods

    MethodDescription
    Exploits VulnerabilityMay exploit Windows vulnerabilities to spread to target computers.
    Network SharesMay spread to network shares with weak passwords.
    Network ScanningScans for open ports on the network.

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