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WORM_NUSUMP.B

February 18, 2011
 ALIASES:

Symantec: W32.SillyIRC; Microsoft: Worm:Win32/Nusump; Kaspersky: Trojan.Win32.VBKrypt.jgg

 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


This worm arrives via removable drives. It may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.

It adds registry entries to enable its automatic execution at every system startup.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size:

86,016 bytes

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

10 Dec 2010

Arrival Details

This worm arrives via removable drives.

It may be dropped by other malware.

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 Temp%\{random name}.exe

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp 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
Windows = %User Temp%\{random name}.exe

HKEY_LOCAL_MACHINE\Software\Microsoft\
Active Setup\Installed Components\{36A5A0DB-297E-FDE2-0501-060104070800}
StubPath = %User Temp%\{random name}.exe

Propagation

This worm creates the following folders in all removable drives:

  • {random name}

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

  • {random name}\{random name}.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]
;{garbage}
Open = .\{random folder name}\{random file name}.exe
;{garbage}
shell\open\Command = {random folder name}\{random file name}.exe
;{garbage}
shell\explore\Command = {random folder name}\{random file name}.exe
;{garbage}
UseAutoPlay=1

Backdoor Routine

This worm connects to the following websites to send and receive information:

  • http://{BLOCKED}s-call.com/index.php?{parameters}

  SOLUTION

Minimum Scan Engine:

8.900

VSAPI PATTERN File:

under testing

Step 1

For Windows ME and XP users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Scan your computer with your Trend Micro product and note files detected as WORM_NUSUMP.B

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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
    • Windows = %User Temp%\{random name}.exe

Step 5

Delete this registry key

[ 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\Active Setup\Installed Components
    • {36A5A0DB-297E-FDE2-0501-060104070800}

Step 6

Search and delete AUTORUN.INF files created by WORM_NUSUMP.B that contain these strings

[ Learn More ]
[Autorun]
;{garbage}
Open = .\{random folder name}\{random file name}.exe
;{garbage}
shell\open\Command = {random folder name}\{random file name}.exe
;{garbage}
shell\explore\Command = {random folder name}\{random file name}.exe
;{garbage}
UseAutoPlay=1

Step 7

Search and delete this folder

[ 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}:\{random name}

Step 8

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