BKDR_KASIDET.TEH

October 14, 2015
 Analysis by: RonJay Kristoffer Caragay
 ALIASES:

Worm:Win32/Kasidet (Microsoft); Backdoor.Win32.Kasidet.ctj (Kaspersky); Mal/Wonton-BB (Sophos)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • 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.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

293,888 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

02 Oct 2015

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 adds the following folders:

  • %Application Data%\alFSVWJB

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

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

  • %Application Data%\alFSVWJB\{random filename}.exe
    where {random filename}.exe is any .exe file found in %Windows% directory

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

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 filename}.exe = "%Application Data%\alFSVWJB\{random filename}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random filename}.exe = "%Application Data%\alFSVWJB\{random filename}.exe"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\N3NNetwork

It adds the following registry entries:

HKEY_CURRENT_USER\Software\N3NNetwork
rate = "{value}"

HKEY_CURRENT_USER\Software\N3NNetwork
{random digits} = "{value}"

HKEY_CURRENT_USER\Software\N3NNetwork
arr = "{value}"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}tva100azxd.com/newfiz7/tasks.php
  • http://{BLOCKED}tva10azxd.com/newfiz7/tasks.php
  • http://{BLOCKED}tva11azxd.com/newfiz7/tasks.php
  • http://{BLOCKED}tva2azxd.com/newfiz7/tasks.php
  • http://{BLOCKED}tva3azxd.com/newfiz7/tasks.php
  • http://{BLOCKED}tva4azxd.com/newfiz7/tasks.php
  • http://{BLOCKED}tva5azxd.com/newfiz7/tasks.php
  • http://{BLOCKED}tva6azxd.com/newfiz7/tasks.php
  • http://{BLOCKED}tva7azxd.com/newfiz7/tasks.php
  • http://{BLOCKED}tva8azxd.com/newfiz7/tasks.php
  • http://{BLOCKED}tva9azxd.com/newfiz7/tasks.php

It deletes itself after execution.

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.954.03

FIRST VSAPI PATTERN DATE:

02 Oct 2015

VSAPI OPR PATTERN File:

11.955.00

VSAPI OPR PATTERN Date:

03 Oct 2015

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 filename}.exe = "%Application Data%\alFSVWJB\{random filename}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random filename}.exe = "%Application Data%\alFSVWJB\{random filename}.exe"

Step 5

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
    • N3NNetwork

Step 6

Search and delete this folder

[ 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.  
  • %Application Data%\alFSVWJB

Step 7

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