TROJ_RIERN.SMA

December 19, 2012
 ALIASES:

Trojan:Win32/Riern.B (Microsoft); Riern (McAfee); Trojan Horse (Symantec); Trojan.Win32.Agent.djej (Kaspersky); Trojan.Win32.Riern.B (v) (Sunbelt); Rootkit.30781 (FSecure)

 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:

136,704 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

24 Nov 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:

  • %User Temp%\1.tmp.exe

(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 creates the following folders:

  • %User Profile%\Application Data\Macromedia
  • %User Profile%\Macromedia\Common

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

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
WAB = "%User Profile%\Common\fe9b600619.exe"

Other System Modifications

This Trojan deletes the following files:

  • %User Temp%\1.tmp

(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 adds the following registry keys:

HKEY_CURRENT_USER\Software\Macromedia

HKEY_CURRENT_USER\Software\AppDataLow\
Software\Macromedia

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Drivers32
midi1 = "%User Profile%\Common\fe9b60061.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Drivers32
wave1 = "%User Profile%\Common\fe9b60061.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Drivers32
aux2 = "%User Profile%\Common\fe9b60061.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Drivers32
mixer1 = "%User Profile%\Common\fe9b60061.dll"

HKEY_CURRENT_USER\Software\Macromedia
fe9b60063 = "{random values}"

HKEY_CURRENT_USER\Software\AppDataLow\
Software\Macromedia
fe9b60063 = "{random values}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Drivers32
wave2 = "%User Profile%\Common\fe9b60061.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Drivers32
aux1 = "%User Profile%\Common\fe9b60061.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Drivers32
mixer2 = "%User Profile%\Common\fe9b60061.dll"

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\2.tmp
  • %User Profile%\Common\fe9b600619.exe
  • %User Profile%\Application Data\Macromedia
  • %User Profile%\Macromedia\Common
  • %User Temp%\fe9b60062.tmp
  • %User Profile%\Common\fe9b60061.dll

(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.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

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 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_CURRENT_USER\Software
    • Macromedia
  • In HKEY_CURRENT_USER\Software\AppDataLow\Software
    • Macromedia

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • WAB = "%User Profile%\Common\fe9b600619.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32
    • midi1 = "%User Profile%\Common\fe9b60061.dll"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32
    • wave1 = "%User Profile%\Common\fe9b60061.dll"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32
    • aux2 = "%User Profile%\Common\fe9b60061.dll"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32
    • mixer1 = "%User Profile%\Common\fe9b60061.dll"
  • In HKEY_CURRENT_USER\Software\Macromedia
    • fe9b60063 = "{random values}"
  • In HKEY_CURRENT_USER\Software\AppDataLow\Software\Macromedia
    • fe9b60063 = "{random values}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32
    • wave2 = "%User Profile%\Common\fe9b60061.dll"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32
    • aux1 = "%User Profile%\Common\fe9b60061.dll"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32
    • mixer2 = "%User Profile%\Common\fe9b60061.dll"

Step 5

Search and delete these components

[ Learn More ]
There may be some components 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.
  • %User Temp%\2.tmp
  • %User Profile%\Common\fe9b600619.exe
  • %User Profile%\Application Data\Macromedia
  • %User Profile%\Macromedia\Common
  • %User Temp%\fe9b60062.tmp
  • %User Profile%\Common\fe9b60061.dll

Step 6

Search and delete these folders

[ 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.
  • %User Profile%\Application Data\Macromedia
  • %User Profile%\Macromedia\Common

Step 7

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

Step 8

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %User Temp%\1.tmp


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