Analysis by: JasperM
 PLATFORM:

Windows 98, ME, NT, 2000, XP, Server 2003

 OVERALL RISK RATING:
 REPORTED INFECTION:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.

  TECHNICAL DETAILS

File Size: 429,056 bytes
File Type: PE
Memory Resident: Yes
Initial Samples Received Date: 26 Jul 2010

Arrival Details

This Trojan may be dropped by other malware.

It may be unknowingly downloaded by a user while visiting malicious websites.

Installation

This Trojan drops the following files:

  • %User Temp%\MSDERUN.EXE - copy of itself
  • %User Temp%\topwesitjh - copy of itself
  • %User Temp%\wscsvc32.exe - detected as TROJ_FAKEAV.SMBE
  • %User Temp%\mschrt20ex.dl - detected as TROJ_FAKEAV.BMH

(Note: %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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It injects codes into the following process(es):

  • EXPLORER.EXE

Other System Modifications

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

HKEY_CLASSES_ROOT\.exe\DefaultIcon
@ = %1

HKEY_CLASSES_ROOT\.exe\shell\
open\command
IsolatedCommand = "%1" %*

HKEY_CLASSES_ROOT\.exe\shell\
runas\command
IsolatedCommand = "%1" %*

HKEY_CLASSES_ROOT\.exe\shell\
runas\command
@ = "%1" %*

HKEY_CLASSES_ROOT\.exe\shell\
start\command
@ = "%1" %*

HKEY_CLASSES_ROOT\.exe\shell\
start\command
IsolatedCommand = "%1" %*

HKEY_CLASSES_ROOT\secfile
Content Type = application/x-msdownload

HKEY_CLASSES_ROOT\secfile
@ = Application

HKEY_CLASSES_ROOT\secfile\DefaultIcon
@ = %1

HKEY_CLASSES_ROOT\secfile\shell\
open\command
IsolatedCommand = "%1" %*

HKEY_CLASSES_ROOT\secfile\shell\
runas\command
IsolatedCommand = "%1" %*

HKEY_CLASSES_ROOT\secfile\shell\
runas\command
@ = "%1" %*

HKEY_CLASSES_ROOT\secfile\shell\
start\command
@ = "%1" %*

HKEY_CLASSES_ROOT\secfile\shell\
start\command
IsolatedCommand = "%1" %*

HKEY_CURRENT_USER\Software
24d1ca9a-a864-4f7b-86fe-495eb56529d8 = ""

HKEY_CURRENT_USER\Software
7bde84a2-f58f-46ec-9eac-f1f90fead080 = ""

HKEY_CURRENT_USER\Software\Classes\
.exe
@ = secfile

HKEY_CURRENT_USER\Software\Classes\
.exe
Content Type = application/x-msdownload

HKEY_CURRENT_USER\Software\Classes\
.exe\DefaultIcon
@ = %1

HKEY_CURRENT_USER\Software\Classes\
.exe\shell\open\
command
IsolatedCommand = "%1" %*

HKEY_CURRENT_USER\Software\Classes\
.exe\shell\runas\
command
IsolatedCommand = "%1" %*

HKEY_CURRENT_USER\Software\Classes\
.exe\shell\runas\
command
@ = "%1" %*

HKEY_CURRENT_USER\Software\Classes\
.exe\shell\start\
command
IsolatedCommand = "%1" %*

HKEY_CURRENT_USER\Software\Classes\
.exe\shell\start\
command
@ = "%1" %*

HKEY_CURRENT_USER\Software\Classes\
secfile
Content Type = application/x-msdownload

HKEY_CURRENT_USER\Software\Classes\
secfile
@ = Application

HKEY_CURRENT_USER\Software\Classes\
secfile\DefaultIcon
@ = %1

HKEY_CURRENT_USER\Software\Classes\
secfile\shell\open\
command
IsolatedCommand = "%1" %*

HKEY_CURRENT_USER\Software\Classes\
secfile\shell\runas\
command
@ = "%1" %*

HKEY_CURRENT_USER\Software\Classes\
secfile\shell\runas\
command
IsolatedCommand = "%1" %*

HKEY_CURRENT_USER\Software\Classes\
secfile\shell\start\
command
IsolatedCommand = "%1" %*

HKEY_CURRENT_USER\Software\Classes\
secfile\shell\start\
command
@ = "%1" %*

It modifies the following registry key(s)/entry(ies) as part of its installation routine:

HKEY_CLASSES_ROOT\.EXE
@ = secfile

(Note: The default value data of the said registry entry is exefile.)

  SOLUTION

Minimum Scan Engine: 8.9

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

Restart in Safe Mode

[ Learn More ]

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.

RESTORE
  • Close Registry Editor.

    • Step 4

    Restore these modified registry values

    [ Learn More ]

    Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

    RESTORE
  • Close Registry Editor.

    • Step 5

    Scan your computer with your Trend Micro product to delete files detected as TROJ_FAKEAV.SMBE. 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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