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BKDR_CFISH.A

May 25, 2017
 Analysis by: Ryan Paolo Maglaque
 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet


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 may be downloaded from remote sites by other malware.

It executes commands from a remote malicious user, effectively compromising the affected system.

As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

418,816 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

01 May 2017

Payload:

Connects to URLs/IPs, Drops files

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.

It may be downloaded from remote site(s) by the following malware:

  • TROJ_CFISH.A

Installation

This Backdoor drops the following copies of itself into the affected system and executes them:

  • %Application Data%\{Random hex values}\chrome.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 drops the following component file(s):

  • %Application Data%\{Random hex values}\{Random values} ← contains the CnC server
  • %Application Data%\{Random hex values}\{Random values} ← contains the modules to download(Keylogger|PasswordStealer|ReverseVNC)

(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%\{Random Hex Values}

(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.)

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
chrome = %Application Data%\{Random hex values}\chrome.exe

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
chrome = %Application Data%\{Random hex values}\chrome.exe

It drops the following files:

  • %User Startup%\chrome.lnk ← Target path = %Application Data%\{Random hex values}\chrome.exe
  • %All Users Profile%\Microsoft\Windows\Start Menu\Programs\Startup\chrome.lnk ← For Win7
  • %All Users Profile%\Start Menu\Programs\Startup\chrome.lnk ← For WinXP

(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.. %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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.)

Backdoor Routine

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

  • Add, remove, or execute modules
  • Download and execute files
  • Change CnC server
  • Execute commands in command line
  • Display a message box
  • Shutdown the machine
  • Update itself
  • Uninstall itself

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}.{BLOCKED}.88.241:8080/index.php/queue/core?m={id}&token={Random Values}

Download Routine

This Backdoor connects to the following URL(s) to download its component file(s):

  • http://{BLOCKED}.{BLOCKED}.88.241:8080/index.php/Keylogger/download?token={Random Values}
  • http://{BLOCKED}.{BLOCKED}.88.241:8080/index.php/PasswordStealer/download?token={Random Values}
  • http://{BLOCKED}.{BLOCKED}.88.241:8080/index.php/ReverseVNC/download?token={Random Values}

As of this writing, the said sites are inaccessible.

Other Details

This Backdoor requires the existence of the following files to properly run:

  • %User Temp%\GID.dat

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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 does the following:

  • Change the file property to hidden after execution

It accepts the following parameters:

  • --update ← update the malware
  • --delay {Number of seconds} ← delay the execution of malware depending on the set number of seconds

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.428.05

FIRST VSAPI PATTERN DATE:

25 May 2017

VSAPI OPR PATTERN File:

13.429.00

VSAPI OPR PATTERN Date:

26 May 2017

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
    • chrome = %Application Data%\{Random hex values}\chrome.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • chrome = %Application Data%\{Random hex values}\chrome.exe

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%\{Random hex values}

Step 6

Search and delete this file

[ 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.
  • %User Startup%\chrome.lnk
  • %All Users Profile%\Microsoft\Windows\Start Menu\Programs\Startup\chrome.lnk
  • %All Users Profile%\Start Menu\Programs\Startup\chrome.lnk

Step 7

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