BKDR_CAPHAW.LEK
Backdoor:Win32/Caphaw.D (Microsoft)
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.
However, as of this writing, the said sites are inaccessible. It deletes itself after execution.
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:
- %Application Data%\{random folder found}\{filename found in %System%}
(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)
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
{random base64 chars} = "%Application Data%\{random folder found}\{filename found in %System%}"
Other System Modifications
This Backdoor adds the following registry keys:
HKEY_CURRENT_USER\Software\Microsoft\
Multimedia\Audio Compression Manager
HKEY_CURRENT_USER\Software\Microsoft\
Multimedia\Audio Compression Manager\MSACM
HKEY_CURRENT_USER\Software\Microsoft\
Multimedia\Audio Compression Manager\Priority v4.00
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.imaadpcm
fdwSupport = 1
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.imaadpcm
cFormatTags = 2
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.imaadpcm
aFormatTagCache = {Value}
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.imaadpcm
cFilterTags = 0
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.msg711
fdwSupport = 1
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.msg711
cFormatTags = 3
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.msg711
aFormatTagCache = {value}
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.msg711
cFilterTags = 0
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.msgsm610
fdwSupport = 1
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.msgsm610
cFormatTags = 2
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.msgsm610
aFormatTagCache = {value}
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.msgsm610
cFilterTags = 0
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.msadpcm
fdwSupport = 1
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.msadpcm
cFormatTags = 2
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.msadpcm
aFormatTagCache = {value}
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.msadpcm
cFilterTags = 0
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.l3acm
fdwSupport = 1
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.l3acm
cFormatTags = 2
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
AudioCompressionManager\DriverCache\msacm.l3acm
aFormatTagCache = {value}
Other Details
This Backdoor connects to the following possibly malicious URL:
- It uses domain generation algorithm (DGA) for its C&C servers. Where the domain could be one of the following:
- http://eoz5u{BLOCKED}mc6r0f.fey.su:443
- http://yv4lfo{BLOCKED}c.exy.su:443
- http://tvlobc{BLOCKED}.enp.cc:443
However, as of this writing, the said sites are inaccessible.
It deletes itself after execution.
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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- {random base64 chars} = "%Application Data%\{random folder found}\{filename found in %System%}"
- {random base64 chars} = "%Application Data%\{random folder found}\{filename found in %System%}"
Step 5
Delete this registry key
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
- AudioCompressionManager
- AudioCompressionManager
- In HKEY_CURRENT_USER\Software\Microsoft\Multimedia
- Audio Compression Manager
- Audio Compression Manager
Step 6
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_CAPHAW.LEK. 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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