Technical Information
To ensure autorun and distribution
Modifies the following registry keys
- [HKCU\Software\Microsoft\Windows\CurrentVersion\Run] 'csrss' = '"%WINDIR%\rss\csrss.exe"'
Creates or modifies the following files
- <SYSTEM32>\tasks\csrss
Sets the following service settings
- [HKLM\System\CurrentControlSet\Services\VBoxWddm] 'ImagePath' = 'VBoxWddm'
- [HKLM\System\CurrentControlSet\Services\VBoxSF] 'ImagePath' = 'VBoxSF'
- [HKLM\System\CurrentControlSet\Services\VBoxMouse] 'ImagePath' = 'VBoxMouse'
- [HKLM\System\CurrentControlSet\Services\VBoxGuest] 'ImagePath' = 'VBoxGuest'
- [HKLM\System\CurrentControlSet\Services\VBoxService] 'ImagePath' = 'VBoxService'
- [HKLM\System\CurrentControlSet\Services\VBoxVideo] 'ImagePath' = 'VBoxVideo'
Creates the following services
- 'VBoxWddm' VBoxWddm
- 'VBoxSF' VBoxSF
- 'VBoxMouse' VBoxMouse
- 'VBoxGuest' VBoxGuest
- 'VBoxService' VBoxService
- 'VBoxVideo' VBoxVideo
Malicious functions
To complicate detection of its presence in the operating system,
adds antivirus exclusion with following registry keys:
- [HKLM\SOFTWARE\Microsoft\Windows Defender\Exclusions\Paths] '%WINDIR%\rss' = '00000000'
- [HKLM\SOFTWARE\Microsoft\Windows Defender\Exclusions\Paths] '%TEMP%\csrss' = '00000000'
- [HKLM\SOFTWARE\Microsoft\Windows Defender\Exclusions\Paths] '%WINDIR%\windefender.exe' = '00000000'
- [HKLM\SOFTWARE\Microsoft\Windows Defender\Exclusions\Paths] '<DRIVERS>' = '00000000'
- [HKLM\SOFTWARE\Microsoft\Windows Defender\Exclusions\Processes] 'csrss.exe' = '00000000'
- [HKLM\SOFTWARE\Microsoft\Windows Defender\Exclusions\Processes] 'windefender.exe' = '00000000'
- [HKLM\SOFTWARE\Microsoft\Windows Defender\Exclusions\Processes] '<File name>.exe' = '00000000'
Executes the following
- '<SYSTEM32>\netsh.exe' advfirewall firewall add rule name="csrss" dir=in action=allow program="%WINDIR%\rss\csrss.exe" enable=yes
Modifies file system
Creates the following files
- %WINDIR%\rss\csrss.exe
- nul
- %TEMP%\csrss\patch.exe
- %TEMP%\csrss\injector\injector.exe
- %TEMP%\csrss\injector\ntquerysysteminformationhook.dll
- %TEMP%\dbghelp.dll
- %TEMP%\symsrv.dll
- %TEMP%\ntkrnlmp.exe
- %TEMP%\osloader.exe
Network activity
UDP
- DNS ASK 28##############18-b868-c5d0d7e9b1d1.uuid.createupdate.org
Miscellaneous
Adds a root certificate
Creates and executes the following
- '%WINDIR%\rss\csrss.exe'
- '%TEMP%\csrss\patch.exe'
- '%TEMP%\csrss\injector\injector.exe' taskmgr.exe %TEMP%\csrss\injector\NtQuerySystemInformationHook.dll
- '<SYSTEM32>\cmd.exe' /C "netsh advfirewall firewall add rule name="csrss" dir=in action=allow program="%WINDIR%\rss\csrss.exe" enable=yes"' (with hidden window)
- '%WINDIR%\rss\csrss.exe' ' (with hidden window)
- '<SYSTEM32>\schtasks.exe' /CREATE /SC ONLOGON /RL HIGHEST /TR "%WINDIR%\rss\csrss.exe" /TN csrss /F' (with hidden window)
- '<SYSTEM32>\schtasks.exe' /delete /tn ScheduledUpdate /f' (with hidden window)
- '%TEMP%\csrss\patch.exe' ' (with hidden window)
- '%TEMP%\csrss\injector\injector.exe' taskmgr.exe %TEMP%\csrss\injector\NtQuerySystemInformationHook.dll' (with hidden window)
Restarts the analyzed sample
Executes the following
- '<SYSTEM32>\cmd.exe' /C "netsh advfirewall firewall add rule name="csrss" dir=in action=allow program="%WINDIR%\rss\csrss.exe" enable=yes"
- '<SYSTEM32>\schtasks.exe' /CREATE /SC ONLOGON /RL HIGHEST /TR "%WINDIR%\rss\csrss.exe" /TN csrss /F
- '<SYSTEM32>\schtasks.exe' /delete /tn ScheduledUpdate /f
