SymbOS.Locknut

Printer Friendly Page

Discovered: February 02, 2005
Updated: February 13, 2007 12:32:47 PM
Also Known As: Locknut.A [F-Secure], SYMBOS_LOCKNUT.A [Trend Micro], SYMBOS_LOCKNUT.B [Trend Micro]
Type: Trojan Horse
Systems Affected: EPOC



SymbOS.Locknut is a Trojan horse program that uses a vulnerability to cause devices running Symbian OS v7.0s to crash. A minor variant of this Trojan also installs a version of SymbOS.Cabir or SymbOS.Cabir.B on the compromised device.

Antivirus Protection Dates

  • Initial Rapid Release version February 02, 2005
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version February 02, 2005
  • Latest Daily Certified version August 09, 2016 revision 001
  • Initial Weekly Certified release date February 02, 2005

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

Writeup By: Robert X Wang

Discovered: February 02, 2005
Updated: February 13, 2007 12:32:47 PM
Also Known As: Locknut.A [F-Secure], SYMBOS_LOCKNUT.A [Trend Micro], SYMBOS_LOCKNUT.B [Trend Micro]
Type: Trojan Horse
Systems Affected: EPOC


When SymbOS.Locknut is executed, it performs the following actions:

  1. Creates some of the following files:

    • [DRIVE LETTER]:\system\apps\gavno\gavno_caption.rsc
    • [DRIVE LETTER]:\system\apps\gavno\gavno.rsc
    • [DRIVE LETTER]:\system\apps\gavno\gavno.app
    • [DRIVE LETTER]:\patch.sis
    • [DRIVE LETTER]:\system\installs\patch.sis
    • [DRIVE LETTER]:\system\installs\patch_v1.sis
    • [DRIVE LETTER]:\system\installs\patch_v2.sis

      Note: When this occurs on Symbian OS v7.0s, some critical system ROM binary files will be overwritten and the device may crash.

  2. Displays the following message:

    App. closed
    AppArcServerTh
    read




  3. May install SymbOS.Cabir or SymbOS.Cabir.B by dropping some of the following files:

    • [DRIVE LETTER]:\system\RECOGS\flo.mdl
    • [DRIVE LETTER]:\system\CARIBESECURITYMANAGER\caribe.sis
    • [DRIVE LETTER]:\system\CARIBESECURITYMANAGER\caribe.rsc
    • [DRIVE LETTER]:\system\CARIBESECURITYMANAGER\caribe.app
    • [DRIVE LETTER]:\system\Apps\caribe\flo.mdl
    • [DRIVE LETTER]:\system\Apps\caribe\caribe.rsc
    • [DRIVE LETTER]:\system\Apps\caribe\caribe.app
    • [DRIVE LETTER]:\system\SYMBIANSECUREDATA\CARIBESECURITYMANAGER\caribe.sis
    • [DRIVE LETTER]:\system\SYMBIANSECUREDATA\CARIBESECURITYMANAGER\caribe.rsc
    • [DRIVE LETTER]:\system\SYMBIANSECUREDATA\CARIBESECURITYMANAGER\caribe.app
    • [DRIVE LETTER]:\system\installs\caribe.sis

      Note: Some variants of caribe.sis also contain SymbOS.Locknut. Therefore SymbOS.Locknut may be sent out with variants of Caribe via Bluetooth.


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: Robert X Wang

Discovered: February 02, 2005
Updated: February 13, 2007 12:32:47 PM
Also Known As: Locknut.A [F-Secure], SYMBOS_LOCKNUT.A [Trend Micro], SYMBOS_LOCKNUT.B [Trend Micro]
Type: Trojan Horse
Systems Affected: EPOC


  1. Install a file manager program on the device.

  2. Enable the option to view the files in the system folder.

  3. Delete the following malicious files:

    • [DRIVE LETTER]:\system\apps\gavno\gavno_caption.rsc
    • [DRIVE LETTER]:\system\apps\gavno\gavno.rsc
    • [DRIVE LETTER]:\system\apps\gavno\gavno.app
    • [DRIVE LETTER]:\patch.sis
    • [DRIVE LETTER]:\system\installs\patch.sis
    • [DRIVE LETTER]:\system\installs\patch_v1.sis
    • [DRIVE LETTER]:\system\installs\patch_v2.sis
    • [DRIVE LETTER]:\system\RECOGS\flo.mdl
    • [DRIVE LETTER]:\system\CARIBESECURITYMANAGER\caribe.sis
    • [DRIVE LETTER]:\system\CARIBESECURITYMANAGER\caribe.rsc
    • [DRIVE LETTER]:\system\CARIBESECURITYMANAGER\caribe.app
    • [DRIVE LETTER]:\system\Apps\caribe\flo.mdl
    • [DRIVE LETTER]:\system\Apps\caribe\caribe.rsc
    • [DRIVE LETTER]:\system\Apps\caribe\caribe.app
    • [DRIVE LETTER]:\system\SYMBIANSECUREDATA\CARIBESECURITYMANAGER\caribe.sis
    • [DRIVE LETTER]:\system\SYMBIANSECUREDATA\CARIBESECURITYMANAGER\caribe.rsc
    • [DRIVE LETTER]:\system\SYMBIANSECUREDATA\CARIBESECURITYMANAGER\caribe.app
    • [DRIVE LETTER]:\system\installs\caribe.sis

      Note: You cannot delete the file CARIBE.RSC when the program is running. If you cannot delete this file, delete all the other files, restart the phone, and then delete the CARIBE.RSC file.

  4. Exit the file manager.

Writeup By: Robert X Wang