Analysis by: Karl Dominguez

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Propagates via removable drives

This worm arrives via removable drives.

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: 115,200 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 25 Apr 2011
Payload: Drops files

Arrival Details

This worm arrives via removable drives.

Installation

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

  • %User Profile%\{random characters}.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 injects threads into the following normal process(es):

  • Explorer.exe

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 = "%User Profile%\{random characters}.exe"

Propagation

This worm creates the following folders in all removable drives:

  • [drive letter]:\kratakje

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

  • [drive letter]:\kratakje\tospoj.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]
USEAUTOPLAY=1
^
shellexecute=kratakje\\tospoj.exe
shell\Install\command=kratakje\\tospoj.exe
shell\open\command=kratakje\\tospoj.exe
shell\explore\command=kratakje\\tospoj.exe
Shell\open\command=kratakje\\tospoj.exe
open=kratakje\\tospoj.exe
Icon=kratakje\\tospoj.exe
action=Open folder to view files using Windows Explore

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 8.118.07
FIRST VSAPI PATTERN DATE: 25 Apr 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

Identify and delete files detected as WORM_RIMECUD.SMB1 using either the Startup Disk or Recovery Console

[ 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 NT\CurrentVersion\Winlogon
    • Taskman  = "%User Profile%\{random characters}.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]:\kratakje

Step 5

Search and delete AUTORUN.INF files created by WORM_RIMECUD.SMB1 that contain these strings

[ Learn More ]
[autorun]
USEAUTOPLAY=1
^
shellexecute=kratakje\\tospoj.exe
shell\Install\command=kratakje\\tospoj.exe
shell\open\command=kratakje\\tospoj.exe
shell\explore\command=kratakje\\tospoj.exe
Shell\open\command=kratakje\\tospoj.exe
open=kratakje\\tospoj.exe
Icon=kratakje\\tospoj.exe
action=Open folder to view files using Windows Explore

Step 6

Scan your computer with your Trend Micro product to delete files detected as WORM_RIMECUD.SMB1. 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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