BKDR_TORLOAD.A
Windows
Threat Type: Backdoor
Destructiveness: No
Encrypted:
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 executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.
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 file(s)/component(s):
- {Current Malware Path, Name, and Extension}.mui <- contains the Tor URL
It adds the following mutexes to ensure that only one of its copies runs at any one time:
- Global\{GUID generated using the affected system's computer name}
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
Local Security Authority = "%Windows%\lsasvs.exe"
Backdoor Routine
This Backdoor executes the following commands from a remote malicious user:
- Execute arbitrary shell codes
- Download and Execute arbitrary files
- May receive download URLs with the following protocol: FTP, HTTP, HTTPS
- if the download has ".jpg" extension, it saves it as ".exe" and execute
- if the download as ".png" extension, it saves it as ".dll" and loads as a library
- Change the time delay for every connection
It connects to the following websites to send and receive information:
- {BLOCKED}ms2ivmt5og.onion
Other Details
This Backdoor requires the following additional components to properly run:
- {Current Malware Path}\TaskHost\Tor\taskhosts.exe <- Tor client to access Tor URL
- {Current Malware Path}\lsass.bin <- contains the TOR client package and its components
It does the following:
- Installs the Tor client from the bin component
- Sleeps for 24hrs after every connection
- Grants standard access rights to the group "EVERYONE"
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\Windows\CurrentVersion\Run
- Local Security Authority = "%Windows%\lsasvs.exe"
- Local Security Authority = "%Windows%\lsasvs.exe"
Step 5
Search and delete this folder
- {Current Malware Path}\TaskHost
Step 6
Search and delete these files
- {Current Malware Path, Name, and Extension}.mui
- {Current Malware Path}\lsass.bin
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_TORLOAD.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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