BKDR_RINBOT.B

Malware type: Backdoor

Aliases: Backdoor.Win32.IRCBot.yc (Kaspersky), BackDoor-DKV (McAfee), Backdoor.IRC.Bot (Symantec), Worm/IrcBot.87552 (Avira), Mal/Packer (Sophos),

In the wild: Yes

Destructive: No

Language: English

Platform: Windows 98, ME, NT, 2000, XP, Server 2003

Encrypted: No

Overall risk rating:

Reported infections:

Damage potential:

High

Distribution potential:

Low

Description: 

To get a one-glance comprehensive view of the behavior of this malware, refer to the Behavior Diagram shown below.

BKDR_RINBOT.B Behavior Diagram

Malware Overview

This memory-resident backdoor is usually dropped or downloaded by other malware.

Using a random TCP port, it connects to an Internet Relay Chat (IRC) server, where it joins an IRC channel. Once a connection is established, it waits for commands from a remote malicious user. The said routine provides the remote user virtual control over the affected system, thus compromising system security.

For additional information about this threat, see:

Description created: Feb. 8, 2007 11:13:01 AM GMT -0800


TECHNICAL DETAILS


File type: PE

Memory resident:  Yes

Size of malware: 87,552 Bytes (compressed)

Ports used: Random TCP ports

Initial samples received on: Feb 8, 2007

Compression type: ExeCryptor

Details:

This backdoor arrives on a system as a file dropped or downloaded by other malware.

Upon execution, it drops a copy of itself as DYDHCP.EXE in the Windows system folder.

It then creates the following registry entry to ensure its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\
CurrentVersion\Run
Dynamic DHCP = "%System%\dydhcp.exe"

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Using a random TCP port, it connects to an Internet Relay Chat (IRC) server, where it joins an IRC channel. Once a connection is established, it waits for the following commands from a remote malicious user:

  • Create, execute, and delete files
  • Download files from the Internet
  • Download an updated copy of itself

The said routine provides the remote user virtual control over the affected system, thus compromising system security.

This backdoor affects systems running on Windows 98, ME, NT, 2000, XP, and Server 2003.

Analysis By: Michael M. Ramirez

Revision History:

First pattern file version: 4.258.02
First pattern file release date: Feb 08, 2007

SOLUTION


Minimum scan engine version needed: 8.000

Pattern file needed: 4.259.00

Pattern release date: Feb 8, 2007


Important note: The "Minimum scan engine" refers to the earliest Trend Micro scan engine version guaranteed to detect this threat. However, Trend Micro strongly recommends that you update to the latest version in order to get comprehensive protection. Download the latest scan engine here.

Solution:

Terminating the Malware Program

This procedure terminates the running malware process.

  1. Open Windows Task Manager.
    • On Windows 98 and ME, press
    CTRL%20ALT%20DELETE
    • On Windows NT, 2000, XP, and Server 2003, press
    CTRL%20SHIFT%20ESC, then click the Processes tab.
  2. In the list of running programs*, locate the process:
    dydhcp.exe
  3. Select the malware process, then press either the End Task or the End Process button, depending on the version of Windows on your computer.
  4. To check if the malware process has been terminated, close Task Manager, and then open it again.
  5. Close Task Manager.

*NOTE: On computers running Windows 98 and ME, Windows Task Manager may not show certain processes. You can use a third party process viewer such as Process Explorer to terminate the malware process.

On computers running all Windows platforms, if the process you are looking for is not in the list displayed by Task Manager or Process Explorer, continue with the next solution procedure, noting additional instructions. If the malware process is in the list displayed by either Task Manager or Process Explorer, but you are unable to terminate it, restart your computer in safe mode.

Editing the Registry

This malware modifies the computer's registry. Users affected by this malware may need to modify or delete specific registry keys or entries. For detailed information regarding registry editing, please refer to the following articles from Microsoft:

  1. HOW TO: Backup, Edit, and Restore the Registry in Windows 95, Windows 98, and Windows ME
  2. HOW TO: Backup, Edit, and Restore the Registry in Windows NT 4.0
  3. HOW TO: Backup, Edit, and Restore the Registry in Windows 2000
  4. HOW TO: Back Up, Edit, and Restore the Registry in Windows XP and Server 2003

Removing Autostart Entry from the Registry

Removing the autostart entry from the registry prevents the malware from executing at startup.

If the registry entry below is not found, the malware may not have executed as of detection. If so, proceed to the succeeding solution set.

  1. Open Registry Editor. Click Start>Run, type REGEDIT, then press Enter.
  2. In the left panel, double-click the following:
    HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>
    Windows>CurrentVersion>Run
  3. In the right panel, locate and delete the entry:
    Dynamic DHCP = "%System%\dydhcp.exe"
    (Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, and C:\Windows\System32 on Windows XP and Server 2003.)
  4. Close Registry Editor.

Important Windows ME/XP Cleaning Instructions

Users running Windows ME and XP must disable System Restore to allow full scanning of infected computers.

Users running other Windows versions can proceed with the succeeding solution set(s).

Running Trend Micro Antivirus

If you are currently running in safe mode, please restart your computer normally before performing the following solution.

Scan your computer with Trend Micro antivirus and delete files detected as BKDR_RINBOT.B. To do this, Trend Micro customers must download the latest virus pattern file and scan their computer. Other Internet users can use HouseCall, the Trend Micro online virus scanner.




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