BKDR_BIFROSE.WINR
Backdoor:Win32/Bifrose.HZ (Microsoft), Backdoor.Win32.Bifrose (Ikarus), BackDoor.Bifrost.19762 (DrWeb)
Windows
Threat Type: Backdoor
Destructiveness: No
Encrypted: No
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 runs certain commands that it receives remotely from a malicious user. Doing this puts the affected computer and information found on the computer at greater risk.
It logs a user's keystrokes to steal information.
It deletes the initially executed copy of itself.
TECHNICAL DETAILS
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:
- %Program Files%\system32\win32.exe
(Note: %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)
It adds the following processes:
- iexplore.exe
It creates the following folders:
- %Program Files%\system32
(Note: %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)
It stays memory-resident by creating remote threads:
- explorer.exe
Autostart Technique
This backdoor adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{UID}
stubpath = "%Program Files%\system32\win32.exe s"
Other System Modifications
This backdoor adds the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{UID}
HKEY_LOCAL_MACHINE\SOFTWARE\Bifrost
HKEY_CURRENT_USER\Software\Bifrost
It adds the following registry entries as part of its installation routine:
HKEY_LOCAL_MACHINE\SOFTWARE\Bifrost
nck = "{hex values}"
HKEY_CURRENT_USER\Software\Bifrost
klg = "01"
Backdoor Routine
This backdoor executes the following command(s) from a remote malicious user:
- Send keystrokes by uploading contents of %Program Files%\system32\logg.dat
- Open a file
- Delete a file
- Rename a file
- Move a file
- Enumerate all running processes
- Start a process
- Terminate a process
- Manipulate registry data
- Get file details
- Capture screenshot or webcam image
- Execute a command line
(Note: %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)
It connects to the following URL(s) to send and receive commands from a remote malicious user:
- 204.95.99.23
Dropping Routine
This backdoor drops the following file(s), which it uses for its keylogging routine:
- %Program Files%\system32\logg.dat
(Note: %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)
Information Theft
This backdoor logs a user's keystrokes to steal information.
Other Details
This backdoor deletes the initially executed copy of itself
SOLUTION
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\Active Setup\Installed Components\{UID}
- stubpath = "%Program Files%\system32\win32.exe s"
- stubpath = "%Program Files%\system32\win32.exe s"
Step 5
Delete this registry key
=Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator’s help. You may also check out this Microsoft article first before modifying your computer's registry.
- In HKEY_LOCAL_MACHINE\SOFTWARE
- Bifrost
- Bifrost
- In HKEY_CURRENT_USER\Software
- Bifrost
- Bifrost
Step 6
Search and delete these folders
- %Program Files%\system32
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_BIFROSE.WINR. 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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