BackDoor-CXT

This page shows details and results of our analysis on the malware BackDoor-CXT

Overview

This is a trojan detection. Unlike viruses, trojans do not self-replicate. They are spread manually, often under the premise that they are beneficial or wanted. The most common installation methods involve system or security exploitation, and unsuspecting users manually executing unknown programs. Distribution channels include email, malicious or hacked web pages, Internet Relay Chat (IRC), peer-to-peer networks, etc.


Minimum Engine

5600.1067

File Length

varies

Description Added

2006-02-15

Description Modified

2006-02-21

Malware Proliferation

Characteristics

This trojan is a remote access trojan. There are several variants of this trojan, and the specific actions taken are decided by the hacker who uses this trojan. The description is a general guide. Newer variant requires the latest DATs for detection.

Upon execution, the trojan drops itself to the following paths.

  • %WINDIR%\system32\nvsvcd.exe
  • %WINDIR%\system\smss.exe
  • C:\documents and settings\%USER%\local settings\temp\smssb.exe
  • C:\documents and settings\%USER%\local settings\temp\smss.exe

It creates the run registry keys to load itself at system startup.

  • HKEY_LOCAL_MACHINE\software\microsoft\windows\currentversion\run \.nvsvc="%WINDIR%\system\smss.exe /w"
  • HKEY_LOCAL_MACHINE\software\microsoft\windows\currentversion\run \.nvsvcb="C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\smssb.exe /u"

The trojan adds the following registry entries.

  • HKEY_CURRENT_USER\software\microsoft\windows\currentversion \internet settings\zonemap\\proxybypass="1"
  • HKEY_CURRENT_USER\software\microsoft\windows\currentversion \internet settings\zonemap\\intranetname="1"
  • HKEY_CURRENT_USER\software\microsoft\windows\currentversion \internet settings\zonemap\\uncasintranet="1"
  • HKEY_LOCAL_MACHINE\system\currentcontrolset\services\windows log \security\security="(binary registry data)
  • HKEY_LOCAL_MACHINE\system\currentcontrolset\services\windows log \errorcontrol="1"
  • HKEY_LOCAL_MACHINE\system\currentcontrolset\services\windows log \objectname="LocalSystem"
  • HKEY_LOCAL_MACHINE\system\currentcontrolset\services\windows log \security
  • HKEY_LOCAL_MACHINE\system\currentcontrolset\services\windows log \type="16"
  • HKEY_LOCAL_MACHINE\system\currentcontrolset\services\windows log \start="2"
  • HKEY_LOCAL_MACHINE\system\currentcontrolset\services\windows log \imagepath="%WINDIR%\system32\nvsvcd.exe"
  • HKEY_LOCAL_MACHINE\system\currentcontrolset\services\windows log \displayname="Windows Log"

The trojan attempts to terminate the following security services.

  • KAVPersonal50
  • kavsvc
  • navapsvc
  • Outpost
  • SAVScan
  • Symantec Core LC
  • WindowsFirewall
  • winroute.exe
  • wrctrl.exe
  • wscsvc
  • wuauserv
  • ZoneAlarm

The backdoor opens a random tcp port and waits commands. It also connects IRC channel to the following remote servers.

  • mdboc.com
  • mdlod.com
  • ledamog.com

The trojan is able to relay spam messages to mail servers at the following domains.

  • aol.com
  • gmail.com
  • hotmail.com
  • netscape.com
  • yahoo.com

The trojan attempts to update itself if a new version is available at rizalof.com.

Symptoms

  • Unexpected IRC/SMTP connections
  • Unexpected port open
  • Presence of the mentioned registry keys
  • Presence of the mentioned files
  • Termination of the mentioned services

Method of Infection

Trojans do not self-replicate. They are spread manually, often under the premise that the executable is something beneficial. Distribution channels include IRC, peer-to-peer networks, newsgroup postings, email, etc.

Removal

All Users:
Use current engine and DAT files for detection and removal.

Modifications made to the system Registry and/or INI files for the purposes of hooking system startup, will be successfully removed if cleaning with the recommended engine and DAT combination (or higher).

But in some particular cases, the following steps need to be taken.

Please go to the Microsoft Recovery Console and restore a clean MBR.

On Windows XP:

  • Insert the Windows XP CD into the CD-ROM drive and restart the computer.
  • When the "Welcome to Setup" screen appears, press R to start the Recovery Console.
  • Select the Windows installation that is compromised and provide the administrator password.
  • Issue 'fixmbr' command to restore the Master Boot Record
  • Follow onscreen instructions.
  • Reset and remove the CD from CD-ROM drive.


On Windows Vista and 7:

  • Insert the Windows CD into the CD-ROM drive and restart the computer.
  • Click on "Repair Your Computer".
  • When the System Recovery Options dialog comes up, choose the Command Prompt.
  • Issue 'bootrec /fixmbr' command to restore the Master Boot Record.
  • Follow onscreen instructions.
  • Reset and remove the CD from CD-ROM drive.

Variants