Analysis by: Kathleen Notario
 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 copies of itself in all 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: 99,328 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 19 Nov 2010

Installation

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

  • %Application Data%\nlwyet.exe

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

It is injected into the following processes running in memory:

  • 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 = %Application Data%\nlwyet.exe

Propagation

This worm drops copies of itself in all 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.

The said .INF file contains the following strings:

{garbage characters}
[autorun]
shell\Install\command=SVJETLA\grada.exe
shell\open\command=SVJETLA\grada.exe
shell\explore\command=SVJETLA\grada.exe
Shell\open\command=SVJETLA\grada.exe
useautoplay=1
shellexecute=SVJETLA\grada.exe
open=SVJETLA\grada.exe
action=Open folder to view files
icon=shell32.dll,4

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 7.634.07
FIRST VSAPI PATTERN DATE: 19 Nov 2010

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

Restart in Safe Mode

[ 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 = %Application Data%\nlwyet.exe

Step 4

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

[ Learn More ]
{garbage characters}
[autorun]
shell\Install\command=SVJETLA\grada.exe
shell\open\command=SVJETLA\grada.exe
shell\explore\command=SVJETLA\grada.exe
Shell\open\command=SVJETLA\grada.exe
useautoplay=1
shellexecute=SVJETLA\grada.exe
open=SVJETLA\grada.exe
action=Open folder to view files
icon=shell32.dll,4

Step 5

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


Did this description help? Tell us how we did.