WORM_RIMECUD.ZDL

October 09, 2012
 Analysis by: Erika Bianca Mendoza
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Propagates via flashdrives

This worm arrives by connecting affected removable drives to a system. It may be unknowingly downloaded by a user while visiting malicious websites.

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:

139,264 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

31 Dec 2011

Payload:

Connects to URLs/IPs

Arrival Details

This worm arrives by connecting affected removable drives to a system.

It may be unknowingly downloaded by a user while visiting malicious websites.

Installation

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

  • %User Profile%\wtylgn.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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • Fda%+10

It injects itself into the following processes as part of its memory residency routine:

  • svchost.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%\wtylgn.exe

Propagation

This worm creates the following folders in all removable drives:

  • boost

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

  • boost\picasso.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=boost/picasso.exe
Shellfjefjkwelfewfhjl
shell\Explore\command=boost/picasso.exe
shell\Open\command=boost/picasso.exe
icon=boost/picasso.exe
open=boost//picasso.exe
action=0pen folder to view files using Windows Explorer

Backdoor Routine

This worm connects to the following URL(s) to send and receive commands from a remote malicious user:

  • {BLOCKED}e.{BLOCKED}usenumber.com
  • {BLOCKED}k.{BLOCKED}-protection.net.ru
  • {BLOCKED}d.{BLOCKED}udio.ru
  • {BLOCKED}a.{BLOCKED}nds.su
  • {BLOCKED}l.{BLOCKED}owerbord.com

NOTES:

Once the backdoor connection is established, it may perform several commands sent by the remote computer. It may include the following:

  • download and execute files
  • start USB propagation

  SOLUTION

Minimum Scan Engine:

9.200

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 = %User Profile%\wtylgn.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.
  • [removable drive]\boost

Step 5

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

[ Learn More ]
[autorun]
USEAUTOPLAY=1
shellexecute=boost/picasso.exe
Shellfjefjkwelfewfhjl
shell\Explore\command=boost/picasso.exe
shell\Open\command=boost/picasso.exe
icon=boost/picasso.exe
open=boost//picasso.exe
action=0pen folder to view files using Windows Explorer

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_RIMECUD.ZDL. 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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