Analysis by: Sabrina Lei Sioting
 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 drops its component files in all removable drives. The dropped AUTORUN.INF is detected by Trend Micro as Mal_Otorun1.

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: 94,208 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 24 Jun 2011

Installation

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

  • %System Root%\RECYCLER\S-1-5-21-6366383742-6125457035-156930196-8614\winmap.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It drops the following file(s)/component(s):

  • %System Root%\RECYCLER\S-1-5-21-6366383742-6125457035-156930196-8614\Desktop.ini
  • %drive letter%\RECYCLER\Desktop.ini

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It creates the following folders:

  • %System Root%\RECYCLER\S-1-5-21-6366383742-6125457035-156930196-8614

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Taskman = "%System Root%\RECYCLER\S-1-5-21-6366383742-6125457035-156930196-8614\winmap.exe"

Propagation

This worm creates the following folders in all removable drives:

  • RECYCLER

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

  • RECYCLER\autorun.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=RECYCLER\autorun.exe
icon=%SystemRoot%\system32\SHELL32.dll,4
action=Open folder to view files
shell\open=Open
shell\open\command=RECYCLER\autorun.exe
shell\open\default=1

NOTES:
It drops its component files in all removable drives. The dropped AUTORUN.INF is detected by Trend Micro as Mal_Otorun1.

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 8.246.03
FIRST VSAPI PATTERN DATE: 24 Jun 2011

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_RIMECUD.AA

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 NT\CurrentVersion\Winlogon
    • Taskman = %System Root%\RECYCLER\S-1-5-21-6366383742-6125457035-156930196-8614\winmap.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.
  • %System Root%\RECYCLER\S-1-5-21-6366383742-6125457035-156930196-8614
  • %drive letter%\RECYCLER

Step 5

Search and delete AUTORUN.INF files created by WORM_RIMECUD.AA that contain these strings

[ Learn More ]
[AutoRun]
open=RECYCLER\autorun.exe
icon=%SystemRoot%\system32\SHELL32.dll,4
action=Open folder to view files
shell\open=Open
shell\open\command=RECYCLER\autorun.exe
shell\open\default=1

Step 6

Scan your computer with your Trend Micro product to delete files detected as WORM_RIMECUD.AA. 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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