WORM_IRCBOT.NB

October 08, 2012
 Analysis by: Sabrina Lei Sioting
 ALIASES:

Trojan.Gen (Symantec); Trojan:Win32/Ircbrute (Microsoft); Trojan.Win32.Jorik.SdBot.eb (Kaspersky);

 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Propagates via removable drives

This worm drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

  TECHNICAL DETAILS

File Size:

93,200 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

05 Feb 2011

Installation

This worm drops the following copies of itself into the affected system:

  • %User Temp%\service.exe

(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.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Windows Update = %User Temp%\service.exe

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Services = service.exe

Propagation

This worm creates the following folders in all removable drives:

  • %drive letter%\BACKUP\RESTORE
  • %drive letter%\BACKUP

It drops the following copy(ies) of itself in all removable drives:

  • BACKUP\RESTORE\driver.exe

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[autorun]
open=BACKUP\RESTORE\driver.exe
icon=%SystemRoot%\system32\SHELL32.dll,4
action=Abrir carpeta para ver archivos
shell\open=Open
shell\open\command=BACKUP\RESTORE\driver.exe
shell\open\default=1

NOTES:
The dropped AUTORUN.INF is detected by Trend Micro as TROJ_OTORUN.AB.

  SOLUTION

Minimum Scan Engine:

8.900

VSAPI PATTERN File:

7.812.17

VSAPI PATTERN Date:

05 Feb 2011

VSAPI PATTERN Date:

2/5/2011 12:00:00 AM

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Remove malware files dropped/downloaded by WORM_IRCBOT.NB

     TROJ_OTORUN.AB

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Windows Update = %User Temp%\service.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Windows Services = service.exe

Step 4

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result. %drive letter%\BACKUP

Step 5

Search and delete AUTORUN.INF files created by WORM_IRCBOT.NB that contain these strings

[ Learn More ]
[autorun]
open=BACKUP\RESTORE\driver.exe
icon=%SystemRoot%\system32\SHELL32.dll,4
action=Abrir carpeta para ver archivos
shell\open=Open
shell\open\command=BACKUP\RESTORE\driver.exe
shell\open\default=1

Step 6

Scan your computer with your Trend Micro product to delete files detected as WORM_IRCBOT.NB. 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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