Analysis by: Nice Yutuc
ALIASES:

Trojan-Dropper.Win32.Injector (AVG), Trojan-Dropper.Win32.Injector (Ikarus), Trojan-Dropper.Win32.Injector.bylo (Kasperksy), a variant of Win32/Kryptik.ZBV (NOD32)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 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.

  TECHNICAL DETAILS

File Size: 133,120 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 20 Jan 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 file(s)/component(s):

  • %USERPROFILE%\Application Data\desktop.ini
  • %USERPROFILE%\Application Data\ntuser.dat

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

  • %AppData%\WMPRWISE.EXE

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Microsoft Firewall 2.9 = "%AppData%\WMPRWISE.EXE"

Other System Modifications

This Trojan adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\LowRegistry
SavedLegacySettingsML = "{random value}"

Other Details

This Trojan attempts to access the following websites to download files, which are possibly malicious:

  • http://{BLOCKED}.{BLOCKED}.115.5/stat1.php
  • http://{BLOCKED}.{BLOCKED}.112.152/stat1.php
  • http://{BLOCKED}.{BLOCKED}.226.176/stat1.php
  • http://{BLOCKED}w.ru

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.726.03
FIRST VSAPI PATTERN DATE: 22 Jan 2012
VSAPI OPR PATTERN File: 8.727.00
VSAPI OPR PATTERN Date: 23 Jan 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

Identify and terminate files detected as TROJ_DROPPER.UAE

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 3

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
    • Microsoft Firewall 2.9 = "%AppData%\WMPRWISE.EXE"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\LowRegistry
    • SavedLegacySettingsML = "{random value}"

Step 4

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.
  • %USERPROFILE%\Application Data\desktop.ini
  • %USERPROFILE%\Application Data\ntuser.dat

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_DROPPER.UAE. 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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