WORM_IRCBOT.AHQ

 Analysis by: Kathleen Notario

 ALIASES:

Backdoor: Win32/IRCbot.FY (Microsoft); W32.Yimfoca (Symantec)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW


This worm arrives via removable drives. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It 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:

59,392 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

17 Feb 2012

Arrival Details

This worm arrives via removable drives.

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

  • %User Profile%\M-1-25-8784-4125-7572\winsvc.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

It creates the following folders:

  • %User Profile%\M-1-25-8784-4125-7572

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} 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
Microsoft® Windows Update = "%User Profile%\M-1-25-8784-4125-7572\winsvc.exe"

Other System Modifications

This worm adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%User Profile%\M-1-25-8784-4125-7572\winsvc.exe = "%User Profile%\M-1-25-8784-4125-7572\winsvc.exe:*:Enabled:Microsoft® Windows Update"

Propagation

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

  • windrvs32.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]
icon=%SystemRoot%\system32\SHELL32.dll,4
action=Open folder to view files
shellexecute=windrvs32.exe
UseAutoPlay=1

Other Details

This worm connects to the following possibly malicious URL:

  • {BLOCKED}7.net

NOTES:

It creates the following folder in removable drives:

  • {Removable Drive}:\94728631

It then searches for folders in removable drives and drop copies of itself as {folder name}.EXE inside {Removable Drive}:\951360278. It then sets the attribute of the original folder to Read-Only, Hidden and System. It then creates an .LNK file as {folder name}.LNK that points to the malware copy to trick users into thinking that they are opening the legitimate folder.

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.794.04

FIRST VSAPI PATTERN DATE:

23 Feb 2012

VSAPI OPR PATTERN File:

8.795.00

VSAPI OPR PATTERN Date:

23 Feb 2012

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

Identify and terminate files detected as WORM_IRCBOT.AHQ

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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
    • Microsoft® Windows Update = "%User Profile%\M-1-25-8784-4125-7572\winsvc.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %User Profile%\M-1-25-8784-4125-7572\winsvc.exe = "%User Profile%\M-1-25-8784-4125-7572\winsvc.exe:*:Enabled:Microsoft® Windows Update"

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.
  • %User Profile%\M-1-25-8784-4125-757
  • {Removable Drive}:\94728631

Step 5

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

[ Learn More ]


[autorun]
icon=%SystemRoot%\system32\SHELL32.dll,4
action=Open folder to view files
shellexecute=windrvs32.exe
UseAutoPlay=1

Step 6

Search and delete these files

[ Learn More ]
There may be some component 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.
  • {Removable Drive}:\{folder name}.lnk

Step 7

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

Step 8

  1. Open a command prompt.
    • For Windows 2000, Windows XP, and Windows Server 2003 users, click Start>Run. In the Open input box, type CMD then press Enter.
  2. In the CMD console, type the following:

    ATTRIB [+R | -R] [+A | -A ] [+S | -S] [+H | -H] [+I | -I] [drive:][path][file name] [/S [/D] [/L]]

    Where:
    + Sets an attribute.
    - Clears an attribute
    R Read-only file attribute
    A Archive file attribute
    S System file attribute
    H Hidden file attribute
    I Not content indexed file attribute
    [drive:][path][filename]
    Specifies a file or files for attrib to process
    /S Processes matching files in the current folder and all subfolders.
    /D Processes folders
    /L Work on the attributes of the Symbolic Link versus the target of the Symbolic Link
    Example:
    To unhide all files and folders (including subfolders) in drive D:
    ATTRIB –H D:\* /S /D
  3. Repeat Step 2 for folders and files in other drives or directories.


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