Detectionmediumtest

Potentially Suspicious GrantedAccess Flags On LSASS

Detects process access requests to LSASS process with potentially suspicious access flags

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Florian Roth (Nextron Systems), Roberto Rodriguez (Cyb3rWard0g), Dimitrios Slamaris, Mark Russinovich, Thomas Patzke, Teymur Kheirkhabarov, Sherif Eldeeb, James Dickenson, Aleksey Potapov, oscd.communityCreated Mon Nov 22Updated Wed Nov 29a18dd26b-6450-46de-8c91-9659150cf088windows

Log Source

WindowsProcess Access

ProductWindows← raw: windows

CategoryProcess Access← raw: process_access

Events when a process opens a handle to another process, commonly used for credential dumping via LSASS.

Detection Logic

detection:
    selection_target:
        TargetImage|endswith: '\lsass.exe'
    selection_access:
        - GrantedAccess|endswith:
              # - '10'  # covered in rule 678dfc63-fefb-47a5-a04c-26bcf8cc9f65
              - '30'
              - '50'
              - '70'
              - '90'
              - 'B0'
              - 'D0'
              - 'F0'
              - '18'
              - '38'
              - '58'
              - '78'
              - '98'
              - 'B8'
              - 'D8'
              - 'F8'
              - '1A'
              - '3A'
              - '5A'
              - '7A'
              - '9A'
              - 'BA'
              - 'DA'
              - 'FA'
              - '0x14C2'  # https://github.com/b4rtik/ATPMiniDump/blob/76304f93b390af3bb66e4f451ca16562a479bdc9/ATPMiniDump/ATPMiniDump.c
        - GrantedAccess|startswith:
              - '0x100000'
              - '0x1418'    # car.2019-04-004
              - '0x1438'    # car.2019-04-004
              - '0x143a'    # car.2019-04-004
              - '0x1f0fff'
              - '0x1f1fff'
              - '0x1f2fff'
              - '0x1f3fff'
              - '0x40'
              # - '0x1000'  # minimum access requirements to query basic info from service
              # - '0x1010'    # car.2019-04-004
              # - '0x1400'
              # - '0x1410'    # car.2019-04-004 # Covered by 678dfc63-fefb-47a5-a04c-26bcf8cc9f65
    filter_main_generic:
        # When using this rule. Remove this filter and replace it by the path of the specific AV you use
        SourceImage|contains:
            - ':\Program Files (x86)\'
            - ':\Program Files\'
            - ':\Windows\System32\'
            - ':\Windows\SysWOW64\'
    filter_optional_malwarebytes:
        SourceImage|endswith: ':\ProgramData\MALWAREBYTES\MBAMSERVICE\ctlrupdate\mbupdatr.exe'
    filter_optional_vscode:
        SourceImage|endswith: '\AppData\Local\Programs\Microsoft VS Code\Code.exe'
    filter_main_windefend_1:
        SourceImage|contains: ':\ProgramData\Microsoft\Windows Defender\'
        SourceImage|endswith: '\MsMpEng.exe'
    filter_main_windefend_2:
        CallTrace|contains|all:
            - '|?:\ProgramData\Microsoft\Windows Defender\Definition Updates\{'
            - '}\mpengine.dll+'
        GrantedAccess: '0x1418'
    filter_main_windefend_3:
        CallTrace|contains:
            - '|c:\program files\windows defender\mprtp.dll'
            - '|c:\program files\windows defender\MpClient.dll'
    filter_optional_vmwaretools:
        SourceImage|contains: ':\ProgramData\VMware\VMware Tools\'
        SourceImage|endswith: '\vmtoolsd.exe'
    filter_optional_sysinternals_process_explorer:
        SourceImage|endswith:
            - '\PROCEXP64.EXE'
            - '\PROCEXP.EXE'
        GrantedAccess: '0x40'
    filter_optional_mbami:
        SourceImage|endswith: '\MBAMInstallerService.exe'
        GrantedAccess: '0x40'
    filter_optional_nextron:
        SourceImage|endswith:
            - '\aurora-agent-64.exe'
            - '\aurora-agent.exe'
            - '\thor.exe'
            - '\thor64.exe'
        GrantedAccess: '0x40'
    filter_main_explorer:
        SourceImage|endswith: '\explorer.exe'
        GrantedAccess: '0x401'
    filter_optional_sysinternals_handle:
        SourceImage|endswith:
            - '\handle.exe'
            - '\handle64.exe'
        GrantedAccess: '0x40'
    filter_optional_webex:
        SourceImage|endswith: '\AppData\Local\WebEx\WebexHost.exe'
        GrantedAccess: '0x401'
    filter_optional_steam_apps:
        SourceImage|contains: '\SteamLibrary\steamapps\'
    condition: all of selection_* and not 1 of filter_main_* and not 1 of filter_optional_*