TROJ_REFPRON.JB

 Analysis by: Rhena Inocencio

 ALIASES:

Trojan:Win32/Refpron.gen!A (Microsoft), Trojan Horse (Symantec), Trj/Downloader.MDW (Panda), W32/Downldr2.EJUQ (FProt), Mal/Generic-L (Sophos)

 PLATFORM:

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

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet

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

  TECHNICAL DETAILS

File Size:

186,880 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

17 Oct 2012

Arrival Details

This Trojan 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 Trojan drops the following files:

  • %System%\comsa32.sys - a text file that contains the ID number of the malware
  • %User Temp%\mta{random 5-digit number}.dll - copy of the legitimate file URLMON.DLL

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.. %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 Trojan registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\AFinding
ImagePath = "{Malware Path and File Name}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\AFinding
Type = "10"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\AFinding
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\AFinding
DisplayName = "AFinding"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\AFinding
ObjectName = "Local System"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\AFinding\Security
Security = "{random values}"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\AFinding

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\AFinding\Security

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
WBEM
BuildW = "PlAdkM3dDgnvV+L"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
WBEM
_{first 2 characters of the malware's file name} = "{random value}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
WBEM
ud{random 2 characters} = "{encrypted location of mta{random 5-digit number}.dll}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
WBEM
m{random 2 characters} = "{random value}"

Other Details

This Trojan requires the following additional components to properly run:

  • %System%\drmgs.sys
  • rtl60.bpl - Borland Delphi Library file

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

NOTES:

It attempts to open the file %System%\drmgs.sys.

It uses the following command line parameters:

  • /Uninstall
  • start
  • /Install

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.472.07

FIRST VSAPI PATTERN DATE:

20 Oct 2012

VSAPI OPR PATTERN File:

9.473.00

VSAPI OPR PATTERN Date:

21 Oct 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

Scan your computer with your Trend Micro product and note files detected as TROJ_REFPRON.JB

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_LOCAL_MACHINE\SOFTWARE\Microsoft\WBEM
    • BuildW = "PlAdkM3dDgnvV+L"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WBEM
    • _{first 2 characters of the malware's file name} = "{random value}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WBEM
    • ud{random 2 characters} = "{encrypted location of mta{random 5-digit number}.dll}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WBEM
    • m{random 2 characters} = "{random value}"

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\SYSTEM\CurrentControlSet\Services
    • AFinding

Step 6

Search and delete the file detected as TROJ_REFPRON.JB

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files in the search result.

Step 7

Search and delete these files

[ Learn More ]
There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %System%\comsa32.sys
  • %User Temp%\mta{random 5-digit number}.dll

Step 8

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