WORM_JORIK.PRN

 Analysis by: Jasen Sumalapao

 ALIASES:

Worm:Win32/Rombrast (Microsoft), Trojan.Win32.Jorik.Impolite.q, Trojan.Win32.Jorik.Impolite.q (Kaspersky), Trojan.Gen (Symantec), W32/Autorun.worm.aadc (NAI), W32/Autorun-BYB (Sophos), Trojan.Win32.Generic!BT (Sunbelt), W32/VBTrojan.Dropper.4!Maximus (Authentium), W32/Jorik_Impolite.Q!tr (Fortinet), Trojan.Win32.VBKrypt (Ikarus), a variant of Win32/Injector.TKI trojan (NOD32), Trojan W32/Suspicious_Gen4.AMFPV (Norman), Trojan.Jorik.Impolite.q (VBA32)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003, Windows Vista, Windows 7

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This worm arrives by connecting affected removable drives to a system. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

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:

94,208 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

08 Jul 2012

Arrival Details

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

It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This worm drops a copy of itself in the following folders using different file names:

  • %User Profile%\Application Data\Microsoft\{random filename}.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.)

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
{random value} = %User Profile%\Application Data\Microsoft\{random filename}.exe

Propagation

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

  • {random filename}_a.exe
  • {random filename}_l.exe

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

NOTES:

This worm also create a short cut (*.LNK) files using the folder names in all removable drives and then changes the attributes of all the corresponding folders to hidden.

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

9.244.05

FIRST VSAPI PATTERN DATE:

08 Jul 2012

VSAPI OPR PATTERN File:

9.245.00

VSAPI OPR PATTERN Date:

09 Jul 2012

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 the registry entry with an unknown data 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
    • {random value} = "%User Profile%\Application Data\Microsoft\{random filename}.exe"

Step 4

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