Analysis by: Rhena Inocencio
ALIASES:

Trojan:Win32/Dynamer!dtc (Microsoft), Trojan.Win32.Jorik.IRCbot.vev (Kaspersky), W32.IRCBot (Symantec)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size: 192,512 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 12 Jun 2014
Payload: Connects to URLs/IPs, Compromises system security

Arrival Details

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This backdoor drops the following component file(s):

  • %User Temp%\lpt{number}\driver.bat - adds the autorun registry entry
  • %User Temp%\System\configuration.ini

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It drops the following copies of itself into the affected system:

  • {All Users Profile}\WindowsUpdate\System\Isass.exe (for versions below Vista/Win7)
  • %ProgramData%\WindowsUpdate\System\Isass.exe (for versions Vista/Win7 only)

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This is usually C:\ProgramData in Windows Vista and 7, or C:\Program Files on Windows 2000, XP (32-bit), and Server 2003, or C:\Program Files (x86) on Windows XP (64-bit).)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • afOneCopyMutex

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
System = ""{All Users Profile}\WindowsUpdate\System\Isass.exe" /f" (for versions below Vista/Win7)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
System = ""%ProgramData%\WindowsUpdate\System\Isass.exe" /f" (for versions Vista/Win7 only)

Backdoor Routine

This backdoor connects to any of the following IRC server(s):

  • {BLOCKED}etexplorers.org

It accesses a remote Internet Relay Chat (IRC) server where it receives the following commands from a remote malicious user:

  • Execute command
  • Display bot version
  • Display computer name
  • Display malware path
  • Upload file to specified IP and port
  • Upload file to specified HTTP server
  • Quit the connection

  SOLUTION

Minimum Scan Engine: 9.700

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Restart in Safe Mode

[ Learn More ]

Step 3

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

 
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
    • System = ""{All Users Profile}\WindowsUpdate\System\Isass.exe" /f"(for versions below Vista/Win7)
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
    • System = ""%ProgramData%\WindowsUpdate\System\Isass.exe" /f"(for versions Vista/Win7 only)

Step 4

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Temp%\lpt{number}\driver.bat
  • %User Temp%\System\configuration.ini

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_IRCBOT.WPGY. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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