Analysis by: Cris Nowell Pantanilla
ALIASES:

Trojan.Win32.Buzus.xrmq (Kaspersky), TrojanDownloader:Win32/Small (Microsoft)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 REPORTED INFECTION:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware

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 executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It retrieves specific information from the affected system.

  TECHNICAL DETAILS

File Size: 1,072,128 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 22 Aug 2016
Payload: Steals information

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 copies of itself into the affected system and executes them:

  • %Application Data%\KLMS\klim.exe

(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 creates the following folders:

  • %Application Data%\KLMS

(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 injects codes into the following process(es):

  • iexplore.exe

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
KLIM = "%Application Data%\KLMS\klim.exe"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\MTR
rno1 = "25263.exe"

HKEY_CURRENT_USER\Software\MTR
gn = "25263.exe"

HKEY_CURRENT_USER\Software\MTR
mep = "2632"

HKEY_CURRENT_USER\Software\MTR
api = "2772"

HKEY_CURRENT_USER\Software\MTR
pim = "2776"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • AddAutoFTPToDB
  • CaptureScreen
  • ChromeInject
  • ClearCred
  • CompressArchive
  • CopyMTP
  • DeleteAutoFTPFromDB
  • DeleteFileFromDevice
  • DisableChrome
  • DisableMouseCapture
  • EnableAndLoadCapList
  • GenerateReports
  • GetAutoFTP
  • GetCamlist
  • GetFileMONLIST
  • GetSound
  • GetUSBMONLIST
  • GetWifi
  • GrabFileFromDevice
  • PutFileOnDevice
  • RarFolder
  • SearchMain
  • SendCam
  • SendFileMonLog
  • SendMTPList
  • SendMTPList2
  • SendStartup
  • SendUSBList
  • SendinfoList
  • SignoutSkype
  • SplitMyFile
  • StartFileMonitor
  • StartShell
  • StealUSB
  • StopCam
  • StopFileMonitor
  • StopSearch
  • StopUSBMonitor
  • Uninstall
  • getkey

It connects to the following websites to send and receive information:

  • {blocked}azeh.ddns.net
  • http://{blocked}.{blocked}.150.90:5656/x9/
  • http://{blocked}.{blocked}.150.90:5656/cucumber/

Information Theft

This backdoor retrieves the following information from the affected system:

  • User Name
  • Computer Name
  • OS Version
  • IP Address

  SOLUTION

Minimum Scan Engine: 9.800

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\Run
    • KLIM = "%Application Data%\KLMS\klim.exe"

Step 4

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
    • MTR

Step 5

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. %Application Data%\KLMS

Step 6

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