1. Symantec/
  2. Security Response/
  3. W32.Disttrack


Risk Level 2: Low

August 16, 2012
August 22, 2012 2:07:45 AM
Also Known As:
Infection Length:
Systems Affected:
When the worm is executed, it copies itself to the following network shares:

The worm creates the following files:
  • %System%\trksrv.exe
  • %System%\netinit.exe
  • %System%\drivers\drdisk.sys
  • %System%\[NAME SELECTED FROM LIST].exe

The worm deletes the following file:

    The worm is comprised of several components:
    • Dropper: main component that drops other modules and is the first to infect the system
    • Wiper: module that contains destructive functionality
    • Reporter: module that reports infection information back to the attacker

    The Dropper component has the following functionality:
    • Copies itself to %System%\trksrv.exe
    • Drops the following files embedded into resources:
      • 64-bit Dropper: %System%\trksrv.exe (contained in the “X509” resource)
      • Reporter module: %System%\netinit.exe (contained in the "PKCS7" resource)
      • Wiper module: %System%\[NAME SELECTED FROM LIST].exe (contained in the "PKCS12" resource)
        Note: [NAME SELECTED FROM LIST] may be one of the following:
        • caclsrv
        • certutl
        • clean
        • ctrl
        • dfrag
        • dnslookup
        • dvdquery
        • event
        • extra ct
        • findfile
        • fsutl
        • gpget
        • iissrv
        • ipsecure
        • msinit
        • ntx
        • ntdsutl
        • ntfrsu til
        • ntnw
        • power
        • rdsadmin
        • regsys
        • routeman
        • rrasrv
        • sacses
        • sfmsc
        • sigver
        • smbinit
        • wcscript
    • Copies itself to the following network shares:
    • Creates a job task to execute itself
    • Creates the following service to start itself when Windows starts:
      • Service: TrkSvr
      • DisplayName: Distributed Link Tracking Server
      • ImagePath: %System%\trksvr.exe

    The Wiper module has the following functionality:
    • Deletes the existing driver from the following location and writes a legitimate driver embedded in resources:
      • The device driver is a clean disk driver that enables user-land applications to read and write to disk sectors. The driver is used to overwrite the computer's MBR but is not malicious by itself.
      • The file is digitally signed by “EldoS Corporation".
      • Executes the following commands that collect file names, which will be overwritten and writes them to f1.inf and f2.inf:
        • dir "C:\Documents and Settings\" /s /b /a:-D 2>nul | findstr -i download 2>nul >f1.inf
        • dir "C:\Documents and Settings\" /s /b /a:-D 2>nul | findstr -i document 2>nul >>f1.inf
        • dir C:\Users\ /s /b /a:-D 2>nul | findstr -i download 2>nul >>f1.inf
        • dir C:\Users\ /s /b /a:-D 2>nul | findstr -i document 2>nul >>f1.inf
        • dir C:\Users\ /s /b /a:-D 2>nul | findstr -i picture 2>nul >>f1.inf
        • dir C:\Users\ /s /b /a:-D 2>nul | findstr -i video 2>nul >>f1.inf
        • dir C:\Users\ /s /b /a:-D 2>nul | findstr -i music 2>nul >>f1.inf
        • dir "C:\Documents and Settings\" /s /b /a:-D 2>nul | findstr -i desktop 2>nul >f2.inf
        • dir C:\Users\ /s /b /a:-D 2>nul | findstr -i desktop 2>nul >>f2.inf
        • dir C:\Windows\System32\Drivers /s /b /a:-D 2>nul >>f2.inf
        • dir C:\Windows\System32\Config /s /b /a:-D 2>nul | findstr -v -i systemprofile 2>nul >>f2.inf
        Note: Files from f1.inf and f2.inf will be overwritten with a JPEG image that is located in the Wiper module. Overwritten files are rendered useless and cannot be repaired.
      • The module will overwrite the MBR so that the compromised computer can no longer boot.

      The Reporter module is responsible for sending information about the infection to the attacker. Information is sent as an HTTP GET request and is structured as:

      The following data is sent to the attacker:
      • [DOMAIN] = domain name
      • [MYDATA] = specifies how many files were overwritten
      • [UID] = IP address of the compromised computer
      • [STATE] = random number


      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: Symantec Security Response
      Summary| Technical Details| Removal

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