Analysis by: Jennifer Gumban
ALIASES:

Trojan-PSW.Win32.Tepfer.qokj (Kaspersky), Backdoor:Win32/Kelihos.F (Microsoft)

 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:
 INFORMATION EXPOSURE:

  • 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: 835,072 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 25 Sep 2013

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 possibly malicious files or file components:

  • %System%\DRIVERS\NMnt.sys
  • %System%\Drivers\Fastfat.sys

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

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
NetworkUpdater = "{Malware Path and File Name}"

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
RecordModifiedMax = "{68 Random Characters}"

HKEY_CURRENT_USER\Software\{Chosen Key}\
{Chosen Sub Key}
DBSavedUse = "{Random Hex Values}"

HKEY_CURRENT_USER\Software\{Chosen Key}\
{Chosen Sub Key}
LineLoadedQuick = "{68 Random Characters}"

HKEY_CURRENT_USER\Software\{Chosen Key}\
{Chosen Sub Key}
PersistentLocalizedName = "{Random Hex Values}"

HKEY_CURRENT_USER\Software\{Chosen Key}\
{Chosen Sub Key}
PlatformCompressedValid = "{Random Hex Values}"

HKEY_CURRENT_USER\Software\{Chosen Key}
ActiveModifiedTheme = "{Random Hex Values}"

HKEY_CURRENT_USER\Software\{Chosen Key}
InfoPlayedCurrent = "{Random Hex Values}"

HKEY_CURRENT_USER\Software\{Chosen Key}
SizeCompletedValid = "{68 Random Characters}"

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://de8kh.{BLOCKED}mi.me/calc.exe
  • http://{BLOCKED}p.com/
  • http://{BLOCKED}g.cc/?p={Random Number}

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.302.05
FIRST VSAPI PATTERN DATE: 24 Sep 2013
VSAPI OPR PATTERN File: 10.303.00
VSAPI OPR PATTERN Date: 25 Sep 2013

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.

 
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • RecordModifiedMax = "{68 Random Characters}"
  • In HKEY_CURRENT_USER\Software\{Chosen Key}\{Chosen Sub Key}
    • DBSavedUse = "{Random Hex Values}"
  • In HKEY_CURRENT_USER\Software\{Chosen Key}\{Chosen Sub Key}
    • LineLoadedQuick = "{68 Random Characters}"
  • In HKEY_CURRENT_USER\Software\{Chosen Key}\{Chosen Sub Key}
    • PersistentLocalizedName = "{Random Hex Values}"
  • In HKEY_CURRENT_USER\Software\{Chosen Key}\{Chosen Sub Key}
    • PlatformCompressedValid = "{Random Hex Values}"
  • In HKEY_CURRENT_USER\Software\{Chosen Key}
    • ActiveModifiedTheme = "{Random Hex Values}"
  • In HKEY_CURRENT_USER\Software\{Chosen Key}
    • InfoPlayedCurrent = "{Random Hex Values}"
  • In HKEY_CURRENT_USER\Software\{Chosen Key}
    • SizeCompletedValid = "{68 Random Characters}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • NetworkUpdater = "{Malware Path and File Name}"

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.
  • %System%\DRIVERS\NMnt.sys
  • %System%\Drivers\Fastfat.sys

Step 5

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


Did this description help? Tell us how we did.