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TROJ_DROPPR.SMH

October 08, 2012
 Analysis by: Christopher Daniel So
 Modified by: Kathleen Notario
 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: Yes

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW


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.

It also has rootkit capabilities, which enables it to hide its processes and files from the user.

It modifies the Internet Explorer Zone Settings.

  TECHNICAL DETAILS

File Size:

Varies

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

12 Aug 2010

Payload:

Hides files and processes

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 adds the following folders:

  • %Windows%\efee3f32f

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

It drops the following copies of itself into the affected system:

  • %Windows%\svchost32.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

It injects codes into the following process(es):

  • LSASS.EXE
  • SVCHOST.EXE

Autostart Technique

This Trojan modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = %System%\userinit.exe,%Windows%\{malware filename}.exe,

(Note: The default value data of the said registry entry is %System%\userinit.exe,.)

Other System Modifications

This Trojan adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Network
PID = {computer name}_{random numbers}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
EnableConcurrentSessions = 1

Rootkit Capabilities

This Trojan also has rootkit capabilities, which enables it to hide its processes and files from the user.

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

Dropping Routine

This Trojan drops the following files:

  • %Windows%\efee3f32f\brrve.nls
  • %Windows%\efee3f32f\wrfsf.nls
  • %Windows%\host32.exe - also detected as TROJ_DROPPR.SMH

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

  SOLUTION

Minimum Scan Engine:

8.900

VSAPI OPR PATTERN File:

7.382.05

VSAPI OPR PATTERN Date:

15 Aug 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

Scan your computer with your Trend Micro product and note files detected as TROJ_DROPPR.SMH

Step 3

Identify and delete files detected as TROJ_DROPPR.SMH using the Recovery Console

[ Learn More ]

Step 4

Restore this modified 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
    • From: Userinit=%System%\userinit.exe,%Windows%\{malware filename}.exe,
      To: %System%\userinit.exe,1

Step 5

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\Network
    • PID={computer name}_{random numbers}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • EnableConcurrentSessions=1

Step 6

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. %Windows%\efee3f32f

Step 7

Scan your computer with your Trend Micro product to delete files detected as TROJ_DROPPR.SMH. 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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