BKDR_CFISH.A
Windows
Threat Type: Backdoor
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
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
418,816 bytes
EXE
No
01 May 2017
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
9.850
13.428.05
25 May 2017
13.429.00
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
Step 4
Delete this registry value
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
- 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
- chrome = %Application Data%\{Random hex values}\chrome.exe
Step 5
Search and delete these folders
- %Application Data%\{Random hex values}
Step 6
Search and delete this file
- %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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