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BKDR_KELIHOS.YVO

July 18, 2016
 Analysis by: Mar Philip Elaurza
 ALIASES:

Backdoor:Win32/Kelihos (Microsoft); Backdoor.Win32.Hlux.fite (Kaspersky); Mal/Kelihos-D (Sophos);

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This backdoor 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:

1,256,949 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

06 Jul 2016

Arrival Details

This backdoor 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 backdoor drops the following files:

  • {malware path}\tmp.exe

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{random parameter 1}{random parameter 2} = "{malware path and file name}"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{random IP addresses}/{URI}.htm
    where {URI} can be any of the following:
    • file
    • online
    • main
    • start
    • install
    • login
    • setup
    • welcome
    • search
    • home
    • default
    • index

NOTES:

The autoun registry {random parameter 1} may be any of the following:

  • Network
  • Time
  • CrashReport
  • Connection
  • Database
  • Icon
  • Desktop
  • Tray
  • Video
  • Media

The autorun registry {random parameter 2} may be any of the following:

  • Informer
  • Verifyer
  • Saver
  • Notifyer
  • Checker
  • Updater

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.634.04

FIRST VSAPI PATTERN DATE:

11 Jul 2016

VSAPI OPR PATTERN File:

12.635.00

VSAPI OPR PATTERN Date:

12 Jul 2016

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

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\CurrentVersion\Run
    • {random parameter 1}{random parameter 2} = "{malware path and file name}"

Step 5

Search and delete these files

[ Learn More ]
There may be some 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.  
  • {malware path}\tmp.exe

Step 6

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