W32.Chainsaw.Worm

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Discovered: September 14, 2000
Updated: February 13, 2007 11:59:22 AM
Type: Trojan Horse, Worm


W32.Chainsaw is a network worm. It spreads to shared drives as Chainsaw.exe. The file has the hidden attribute.

Antivirus Protection Dates

  • Initial Rapid Release version September 14, 2000
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version September 14, 2000
  • Latest Daily Certified version September 28, 2010 revision 036

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

Writeup By: David Agosta

Discovered: September 14, 2000
Updated: February 13, 2007 11:59:22 AM
Type: Trojan Horse, Worm


If Chainsaw.exe is run, it creates the Winmine.exe file in the \Windows folder. It also creates the value:

Mines

in the registry key

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run

The first time that the worm is run, it disables the ZoneAlarm firewall program if it is installed. It also posts the following message to the alt.horror newsgroup:

From: Leatherface
Subject: CHAINSAWED
Message: WHO WILL SURVIVE AND WHAT WILL BE LEFT OF THEM?

W32.Chainsaw spreads by randomly picking IP addresses and testing to see if they are infected with SubSeven or NetBus, or if they use NetBIOS. If the test is successful, it uses the backdoor to install and run itself.

The worm also has a random counter that, when triggered, creates a Trojan program. The Trojan overwrites the hard disk with the following text:

THE FILM WHICH YOU ARE ABOUT TO SEE IS AN ACCOUNT OF THE TRAGEDY WHICH BEFELL A GROUP OF FIVE YOUTHS. IN PARTICULAR SALLY HARDESTY AND HER INVALID BROTHER FRANKLIN. IT IS ALL THE MORE TRAGIC IN THAT THEY WERE YOUNG. BUT, HAD THEY LIVED VERY, VERY LONG LIVES, THEY COULD NOT HAVE EXPECTED NOR WOULD THEY HAVE WISHED TO SEE AS MUCH OF THE MAD AND MACABRE AS THEY WERE TO SEE THAT DAY. FOR THEM AN IDYLLIC SUMMER AFTERNOON DRIVE BECAME A NIGHTMARE. THE EVENTS OF THAT DAY WERE TO LEAD TO THE DISCOVERY OF ONE OF THE MOST BIZARRE CRIMES IN THE ANNALS OF AMERICAN HISTORY, THE TEXAS CHAIN SAW MASSACRE...

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: David Agosta

Discovered: September 14, 2000
Updated: February 13, 2007 11:59:22 AM
Type: Trojan Horse, Worm


To remove this worm:

  • Delete Chainsaw.exe and Winmine.exe (restoration of Winmine is optional).
  • Remove the Mines value from the \Run key.
  • Scan with NAV and check for the SubSeven and NetBus Backdoor Trojans.

To delete the worm files:
  1. Click Start, point to Find (or Search), and then click Files or Folders.
  2. Make sure that Look in is set to (C:) and that Include subfolders is checked.
  3. In the Named box, type--or copy and paste--the following file names:

    chainsaw.exe winmine.exe
  4. Click Find Now.
  5. Delete the files that are found.

NOTE: The Winmine.exe file is a Windows game. Reinstallation is optional.

To edit the registry:

CAUTION : We strongly recommend that you back up the system registry before you make any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure that you modify only the keys that are specified. Please see the document How to back up the Windows registry before you proceed.
  1. Click Start, and click Run. The Run dialog box appears.
  2. Type regedit and then click OK. The Registry Editor opens.
  3. Navigate to the following subkey:

    HKEY_CURRENT_USER\Software\Microsoft\
    Windows\CurrentVersion\Run
  4. In the right pane, locate and delete the value:

    Mines
  5. Close the Registry Editor.

To scan with Norton AntiVirus:
  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Start Norton AntiVirus (NAV), and run a full system scan, making sure that NAV is configured to scan all files.
  3. Delete any files that are detected as SubSeven or NetBus.


Writeup By: David Agosta