What is the MSBLAST.B?

Also known as: Blaster.B, WORM_MSBLAST.B, Win32.Poza.C, W32/Lovsan.worm.c, Worm.Win32.Lovesan

Blaster.B.Worm is a variant of Blaster Worm that exploits the DCOM RPC vulnerability (described in Microsoft Security Bulletin MS03-026), using TCP port 135. The worm targets only Windows 2000 and Windows XP machines. While Windows NT and Windows 2003 Server machines are vulnerable to the aforementioned exploit if it is not properly patched, the worm is not coded to replicate to those systems.

This worm attempts to download the penis32.exe file to the %WinDir%\System32 folder, and then execute it. This worm does not have any mass-mailing functionality.

How Does MSBLAST.B Worm Infect My System?

When it is executed, MSBLAST.B performs the following actions:

1. Checks to see whether a computer is already infected and whether the worm is running. If so, the worm will not infect the computer a second time.
   
   
2. Adds the value:
   
   "windows auto update"="penis32.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   
   so that the worm runs when you start Windows.
   
   
3. Generates an IP address and attempts to infect the computer that has that address. The IP address is generated according to the following algorithms:
   
   • For 40% of the time, the generated IP address is of the form A.B.C.0, where A and B are equal to the first two parts of the infected computer's IP address.
     
     C is also calculated by the third part of the infected system's IP address; however, for 40% of the time the worm checks whether C is greater than 20. If so, a random value less than 20 is subtracted from C. Once the IP address is calculated, the worm will attempt to find and exploit a computer with the IP address A.B.C.0.
     
     The worm will then increment the 0 part of the IP address by 1, attempting to find and exploit other computers based on the new IP address, until it reaches 254.
     
     
   • With a probability of 60%, the generated IP address is completely random.
     
     
4. Sends data on TCP port 135, which may exploit the DCOM RPC vulnerability. The worm sends one of two types of data: either to exploit Windows XP or Windows 2000. For 80% of the time, Windows XP data will be sent; and for 20% of the time the Windows 2000 data will be sent.
   
   Notes:
   • The local subnet will become saturated with port 135 requests.
   • While W32.Blaster.Worm cannot spread to the Windows NT or Windows Server 2003, unpatched computers running these operating systems may crash as a result of the worm's attempts to exploit them. However, if the worm is manually placed and executed on a computer running these operating systems, it can run and spread.
   • Due to the random nature of how the worm constructs the exploit data, this may cause the RPC service to crash if it receives incorrect data. This may manifest as svchost.exe, generating errors as a result of the incorrect data.
   • If the RPC service crashes, the default procedure under Windows XP and Windows Server 2003 is to restart the computer. To disable this feature, see step one of the Removal Instructions below.
     
     
5. Uses Cmd.exe to create a hidden remote shell process that will listen on TCP port 4444, allowing an attacker to issue remote commands on an infected system.
   
   
6. Listens on UDP port 69. When the worm receives a request from a computer to which it was able to connect using the DCOM RPC exploit, it will send Penis32.exe to that computer and tell it to execute the worm.
   
   
7. If the current date is the 16th through the end of the month for the months of January to August, or if the current month is September through December, the worm will attempt to perform a DoS on Windows Update. However, the attempt to perform the DoS will succeed only if one the following conditions is true:
   • The worm runs on a Windows XP computer that was either infected or restarted during the payload period.
   • The worm runs on a Windows 2000 computer that was infected during the payload period and has not been restarted since it was infected.
   • The worm runs on a Windows 2000 computer that has been restarted since it was infected, during the payload period, and the currently logged in user is Administrator.
     
     
8. The DoS traffic has the following characteristics:
   • Is a SYN flood on port 80 of windowsupdate.com.
   • Tries to send 50 HTTP packets every second.
   • Each packet is 40 bytes in length.
   • If the worm cannot find a DNS entry for windowsupdate.com, it uses a destination address of 255.255.255.255.
     

Some fixed characteristics of the TCP and IP headers are:
• IP identification = 256
• Time to Live = 128
• Source IP address = a.b.x.y, where a.b are from the host ip and x.y are random. In some cases, a.b are random.
• Destination IP address = dns resolution of "windowsupdate.com"
• TCP Source port is between 1000 and 1999
• TCP Destination port = 80
• TCP Sequence number always has the two low bytes set to 0; the 2 high bytes are random.
• TCP Window size = 16384

How to Remove the MSBLAST.B worm?

Kaspersky Internet Security Can Prevent You From Virus and Intrusion. If Kaspersky detects MSBLAST.B during the scan, it will AUTOMATICALLY offer you the option of deleting it. Do this by following the program's instructions.

Follow these steps in removing the MSBLAST.B worm.

Important: To fully protect systems against this security threat, users are advised to apply the critical patches first before performing the Removal Instructions. The importance of applying these patches cannot be overstated and should be strictly implemented across the network. Failure to apply the specified patches may possibly result to remote attacks. Additionally, cleaning the system without prior installation may result to immediate reinfection or system instability.

1. Applying Patches

Apply the patches issued by Microsoft from the following page: Microsoft Security Bulletin MS03-026

2. RPC DCOM Buffer Overflow Vulnerability Scanning Tool

Advises users to download the scanning tool released by Microsoft that can identify host machines in their network that do not have the MS03-026 security patch installed.

This Microsoft Scanning Tool is available for download at: http://support.microsoft.com?kbid=826369.

3. Terminating the Malware Program

This procedure terminates the running malware process from memory.

1. Open Windows Task Manager press
   CTRL+SHIFT+ESC, and click the Processes tab.
2. In the list of running programs*, locate the process:
   PENIS32.EXE
3. Select the malware process, then press either the the End Process button.
4. To check if the malware process has been terminated, close Task Manager, and then open it again.
5. Close Task Manager.

4. Removing Autostart Entries from the Registry

Removing autostart entries from the registry prevents the malware from executing during startup.

1. Open Registry Editor. To do this, click Start>Run, type Regedit, then press Enter.
2. In the left panel, double-click the following:
   HKEY_LOCAL_MACHINE>Software>Microsoft>
   Windows>CurrentVersion>Run
3. In the right panel, locate and delete the entry:
   "windows auto update" = PENIS32.EXE
4. Close Registry Editor.

5. Updating the Virus Definitions

If you do not know which anti-virus software can provide strong protection for you, Kaspersky Internet Security is recommended.

6. Run a full system scan and delete all the files detected as MSBLAST.B.

1. Start your Kaspersky Internet Security and make sure that it is configured to scan all the files.
2. Run a full system scan.
3. If any files are detected as infected with MSBLAST.B, click Delete.

How to Disinfect My Computer from Worms?

In order to keep your computer protected, bear the following tips in mind:

1. If you have filtering tools installed, configure them to reject messages with the characteristics described above. If, in spite of doing this, you receive the message that contains the virus: do not open it, do not run the attached file and delete it, making sure that you also delete it from the Deleted Items folder.
2. Install a good antivirus in your computer. Select Kaspersky Internet Security to get the Kaspersky antivirus solution that best suits your needs.
3. Keep your antivirus updated. If automatic updates are available, configure your antivirus to use them.
4. Keep your permanent antivirus protection enabled at all times.

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