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TROJ_DROPPR.TVZ

February 21, 2013
 Analysis by: Mark Joseph Manahan
 Modified by: Rhena Inocencio
 ALIASES:

Trojan:Win32/Bublik.B (Microsoft), Trojan.Bebloh (Symantec)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • 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 modifies the Internet Explorer Zone Settings.

  TECHNICAL DETAILS

File Size:

126,464 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

07 Aug 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 copies of itself into the affected system:

  • %System%\{malware file name}.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It injects codes into the following process(es):

  • csrss.exe

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
userinit.exe
Debugger = "{malware file name}.exe"

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}cum.{BLOCKED}tp.com

NOTES:

The file name used for its dropped copy may contain the following strings combined with random characters:

  • def
  • dns
  • exec
  • hlp
  • logon
  • mem
  • mixer
  • mon
  • pack
  • play
  • setup
  • srv
  • user
  • video
  • win

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.308.08

FIRST VSAPI PATTERN DATE:

07 Aug 2012

VSAPI OPR PATTERN File:

9.309.00

VSAPI OPR PATTERN Date:

07 Aug 2012

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

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

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\Windows NT\CurrentVersion\Image File Execution Options\userinit.exe
    • Debugger = "{malware file name}.exe"

Step 5

Reset Internet security settings

[ Learn More ]

Step 6

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