Discovered: December 13, 2006
Updated: February 13, 2007 1:02:49 PM
Type: Worm
Systems Affected: Windows



W32.Sagevo is a worm that spreads by exploiting the Symantec Client Security and Symantec AntiVirus Elevation of Privilege (as described in Symantec Advisory SYM06-010 ). The worm lowers security settings and may download other threats.

Notes:

  • This worm attempts to exploit a previously addressed vulnerability in Symantec Client Security and Symantec Antivirus, SYM06-010; patches for the particular Symantec product vulnerability have been available since Thursday, May 25th, 2006. As a result, customers who have applied the patch in their environment are unaffected by the worm's attempt to leverage the Symantec vulnerability for an attack. Customers running Symantec Client Security or Symantec intrusion prevention (IPS) capable products are protected against all known and unknown exploits of SYM06-010 via IPS signatures released on May 26th, 2006.
  • Symantec highly recommends that users of the affected products patch their systems as soon as they are able to help avoid the spread of this particular Sybot worm family. If systems are infected with W32.Sagevo and this security patch has not been applied please read the document, Attempting to migrate from 10.x to a newer version fails after becoming infected with a worm which exploits SYM06-010.
  • IPS signatures against all known and unknown exploits of SYM06-010 were released on May 26, 2006.
  • Excessive network traffic caused by an infection may result in a significant degradation of network performance.


Antivirus Protection Dates

  • Initial Rapid Release version December 14, 2006
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version December 14, 2006
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date December 20, 2006

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Stephen Doherty

Discovered: December 13, 2006
Updated: February 13, 2007 1:02:49 PM
Type: Worm
Systems Affected: Windows


When W32.Sagevo is executed, it performs the following actions:

  1. Copies itself as the following file:

    %System%\wins\svchost.exe

    Note: %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  2. Attempts to spread using the Symantec Client Security and Symantec AntiVirus Elevation of Privilege (as described in Symantec Advisory SYM06-010).

  3. Creates 512 threads and then attempts to connect to a range of IP addresses on TCP port 2967.

  4. Obtains the IP address of the compromised computer, generates an IP address, and attempts to infect the computer that has that address. The IP address is generated according to the following algorithms:

    • If the IP address is 192.168.C.D, it starts with 192.168.0.1.
    • If the IP address is 10.B.C.D, it starts with 10.0.0.1.
    • If the IP address is not one of the above and the third digit is greater than 11, it must be A.B.C.0. If the third digit is less than 11, the address must be A.B.0.0.

  5. 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. If the IP reaches 240.254.254.254, the worm restarts the infection sequence with 10.0.0.0 again.

  6. Drops the following .bat file and deletes itself:

    %Temp%\NL[RANDOM].bat

  7. Downloads a .bat file from the server and executes it.

At the time of writing, the .bat file performs the following actions:
  1. Attempts to connect to the remote domain ftpd.3322.org through TCP port 21211 and download a copy of Backdoor.Wualess.B as the following file:

    NL.eXe

  2. Attempts to stop the SharedAccess service using the following command:

    net stop SharedAccess


Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

Writeup By: Stephen Doherty

Discovered: December 13, 2006
Updated: February 13, 2007 1:02:49 PM
Type: Worm
Systems Affected: Windows


The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Run a full system scan.
  4. Delete any values added to the registry.
For specific details on each of these steps, read the following instructions.

1. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
Note:
When you are completely finished with the removal procedure and are satisfied that the threat has been removed, reenable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article: Antivirus Tools Cannot Clean Infected Files in the _Restore Folder (Article ID: Q263455).

2. To update the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Running LiveUpdate, which is the easiest way to obtain virus definitions:
    • If you use Norton AntiVirus 2006, Symantec AntiVirus Corporate Edition 10.0, or newer products, LiveUpdate definitions are updated daily. These products include newer technology.
    • If you use Norton AntiVirus 2005, Symantec AntiVirus Corporate Edition 9.0, or earlier products, LiveUpdate definitions are updated weekly. The exception is major outbreaks, when definitions are updated more often.
  • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted daily. You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to Virus Definitions (Intelligent Updater).

    The latest Intelligent Updater virus definitions can be obtained here: Intelligent Updater virus definitions. For detailed instructions read the document: How to update virus definition files using the Intelligent Updater.

3. To run a full system scan
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
  2. Run a full system scan.
  3. If any files are detected, follow the instructions displayed by your antivirus program.

Important: If you are unable to start your Symantec antivirus product or the product reports that it cannot delete a detected file, you may need to stop the risk from running in order to remove it. To do this, run the scan in Safe mode. For instructions, read the document, How to start the computer in Safe Mode . Once you have restarted in Safe mode, run the scan again.

After the files are deleted, restart the computer in Normal mode.

Writeup By: Stephen Doherty