Malicious Software Encyclopedia: Win32/Msblast
Published:
February 2, 2005
The Win32/Msblast family of network worms exploit a Remote Procedure Call (RPC) Distributed Component Object Model (DCOM) vulnerability on Microsoft Windows 2000 and Windows XP systems. The worm may also attempt denial of service (DoS) attacks on some server sites, or create a backdoor program that allows attackers to access the infected system.
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Threat Overview
| Class/type | Worm - Network
|
| Discovered | August 12, 2003 |
| Circulating | Yes |
| Affected operating systems | Windows 2000
Windows XP
|
| Affected software |
Not specified
|
| 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):
CA:
Win32.PozaF-secure:
LovsanGlobal Hauri:
Worm.Win32.BlasterMcAfee:
W32/Lovsan.wormNorman:
W32/BlasterPanda:
BlasterSophos:
W32/BlasterSymantec:
W32.Blaster.WormTrend Micro:
WORM_MSBLAST
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)Technical Analysis
When Win32/MSblast variants run, they create a registry entry under the key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run, so that the worm automatically starts when the system reboots.
The worm then attempts to spread to other systems on the Internet by selecting an IP address, either at random or based on the IP of the infected system, and incrementing that address. The worm attempts to connect to TCP port 135 on the target system and send exploit communication sequence. If the connection is established and the target computer is an unpatched Windows 2000 or Windows XP system, the worm spreads through TCP port 4444 and UDP port 69. The worm skips any IP address that has a part equal to 255.
The worm may perform other actions, including:
DoS attacks against Web sites, including windowsupdate.com, kimble.org, or tuiasi.ro, if the day of the month is greater than 15 or the month of the year is greater than 8.
Changing the Internet Explorer home page.
Opening a backdoor program, listening at a random TCP port, that allows attackers to gain access to the infected system, and reports the port number and infected system IP address to a remote server.
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
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.
How to Tell If Your Computer Is Infected
Some customers whose computers have been infected may not notice the presence of the worm at all, while others who are not infected may experience problems because the worm is attempting to attack their computers. Typical symptoms include Windows XP and Windows Server2003 systems restarting every few minutes without user input, or Windows NT 4.0 and Windows 2000 systems becoming unresponsive.
If your computer is infected, you may see the following error message:
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 vulnerability in RPC DCOM service on Windows 2000 and Windows XP operating systems |
