Sigma detection rules

high

Base64 Encoded PowerShell Command Detected

Detects usage of the "FromBase64String" function in the commandline which is used to decode a base64 encoded string

status test author Florian Roth (Nextron Systems) id e32d4572-9826-4738-b651-95fa63747e8a

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title: Base64 Encoded PowerShell Command Detected
id: e32d4572-9826-4738-b651-95fa63747e8a
status: test
description: Detects usage of the "FromBase64String" function in the commandline which is used to decode a base64 encoded string
references:
    - https://gist.github.com/Neo23x0/6af876ee72b51676c82a2db8d2cd3639
author: Florian Roth (Nextron Systems)
date: 2020-01-29
modified: 2023-01-26
tags:
    - attack.stealth
    - attack.t1027
    - attack.execution
    - attack.t1140
    - attack.t1059.001
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        CommandLine|contains: '::FromBase64String('
    condition: selection
falsepositives:
    - Administrative script libraries
level: high

high

Binary Padding - Linux

Adversaries may use binary padding to add junk data and change the on-disk representation of malware. This rule detect using dd and truncate to add a junk data to file.

status test author Igor Fits, oscd.community id c52a914f-3d8b-4b2a-bb75-b3991e75f8ba

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title: Binary Padding - Linux
id: c52a914f-3d8b-4b2a-bb75-b3991e75f8ba
status: test
description: |
    Adversaries may use binary padding to add junk data and change the on-disk representation of malware.
    This rule detect using dd and truncate to add a junk data to file.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1027.001/T1027.001.md
author: Igor Fits, oscd.community
date: 2020-10-13
modified: 2023-05-03
tags:
    - attack.stealth
    - attack.t1027.001
logsource:
    product: linux
    service: auditd
detection:
    selection_execve:
        type: 'EXECVE'
    keywords_truncate:
        '|all':
            - 'truncate'
            - '-s'
    keywords_dd:
        '|all':
            - 'dd'
            - 'if='
    keywords_filter:
        - 'of='
    condition: selection_execve and (keywords_truncate or (keywords_dd and not keywords_filter))
falsepositives:
    - Unknown
level: high
simulation:
    - type: atomic-red-team
      name: Pad Binary to Change Hash - Linux/macOS dd
      technique: T1027.001
      atomic_guid: ffe2346c-abd5-4b45-a713-bf5f1ebd573a

high

Binary Padding - MacOS

Adversaries may use binary padding to add junk data and change the on-disk representation of malware. This rule detect using dd and truncate to add a junk data to file.

status test author Igor Fits, Mikhail Larin, oscd.community id 95361ce5-c891-4b0a-87ca-e24607884a96

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title: Binary Padding - MacOS
id: 95361ce5-c891-4b0a-87ca-e24607884a96
status: test
description: Adversaries may use binary padding to add junk data and change the on-disk representation of malware. This rule detect using dd and truncate to add a junk data to file.
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1027.001/T1027.001.md
    - https://linux.die.net/man/1/truncate
    - https://linux.die.net/man/1/dd
author: 'Igor Fits, Mikhail Larin, oscd.community'
date: 2020-10-19
modified: 2023-02-17
tags:
    - attack.stealth
    - attack.t1027.001
logsource:
    product: macos
    category: process_creation
detection:
    selection_truncate:
        Image|endswith: '/truncate'
        CommandLine|contains: '-s +'
    selection_dd:
        Image|endswith: '/dd'
        CommandLine|contains:
            - 'if=/dev/zero' # if input is not /dev/zero, then there is no null padding
            - 'if=/dev/random' # high-quality random data
            - 'if=/dev/urandom' # low-quality random data
    condition: 1 of selection_*
falsepositives:
    - Legitimate script work
level: high

high

Csc.EXE Execution Form Potentially Suspicious Parent

Detects a potentially suspicious parent of "csc.exe", which could be a sign of payload delivery.

status test author Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems), X__Junior (Nextron Systems) id b730a276-6b63-41b8-bcf8-55930c8fc6ee

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title: Csc.EXE Execution Form Potentially Suspicious Parent
id: b730a276-6b63-41b8-bcf8-55930c8fc6ee
status: test
description: Detects a potentially suspicious parent of "csc.exe", which could be a sign of payload delivery.
references:
    - https://www.uptycs.com/blog/warzonerat-can-now-evade-with-process-hollowing
    - https://reaqta.com/2017/11/short-journey-darkvnc/
    - https://www.pwc.com/gx/en/issues/cybersecurity/cyber-threat-intelligence/yellow-liderc-ships-its-scripts-delivers-imaploader-malware.html
author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems), X__Junior (Nextron Systems)
date: 2019-02-11
modified: 2026-03-23
tags:
    - attack.execution
    - attack.stealth
    - attack.t1059.005
    - attack.t1059.007
    - attack.t1218.005
    - attack.t1027.004
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\csc.exe'
        - OriginalFileName: 'csc.exe'
    selection_parent_generic:
        ParentImage|endswith:
            - '\cscript.exe'
            - '\excel.exe'
            - '\mshta.exe'
            - '\onenote.exe'
            - '\outlook.exe'
            - '\powerpnt.exe'
            - '\winword.exe'
            - '\wscript.exe'
    selection_parent_powershell:
        ParentImage|endswith:
            - '\powershell.exe'
            - '\pwsh.exe'
        ParentCommandLine|contains:
            - '-Encoded '
            - 'FromBase64String'
    selection_parent_susp_location:
        - ParentCommandLine|re: '(?:[Pp]rogram[Dd]ata|%(?:[Ll]ocal)?[Aa]pp[Dd]ata%|\\[Aa]pp[Dd]ata\\(?:[Ll]ocal(?:[Ll]ow)?|[Rr]oaming))\\[^\\]{1,256}$'
        - ParentCommandLine|contains:
              - ':\PerfLogs\'
              - ':\Users\Public\'
              - ':\Windows\Temp\'
              - '\Temporary Internet'
        - ParentCommandLine|contains|all:
              - ':\Users\'
              - '\Favorites\'
        - ParentCommandLine|contains|all:
              - ':\Users\'
              - '\Favourites\'
        - ParentCommandLine|contains|all:
              - ':\Users\'
              - '\Contacts\'
        - ParentCommandLine|contains|all:
              - ':\Users\'
              - '\Pictures\'
    filter_main_programfiles:
        # Note: this is a generic filter. You could baseline execution in your env for a more robust rule
        ParentImage|startswith:
            - 'C:\Program Files (x86)\' # https://twitter.com/gN3mes1s/status/1206874118282448897
            - 'C:\Program Files\' # https://twitter.com/gN3mes1s/status/1206874118282448897
    filter_main_sdiagnhost:
        ParentImage: 'C:\Windows\System32\sdiagnhost.exe' # https://twitter.com/gN3mes1s/status/1206874118282448897
    filter_main_w3p:
        ParentImage: 'C:\Windows\System32\inetsrv\w3wp.exe' # https://twitter.com/gabriele_pippi/status/1206907900268072962
    filter_optional_chocolatey:
        ParentImage: 'C:\ProgramData\chocolatey\choco.exe' # Chocolatey https://chocolatey.org/
    filter_optional_defender:
        ParentCommandLine|contains: '\ProgramData\Microsoft\Windows Defender Advanced Threat Protection'
    filter_optional_ansible:
        # Note: As ansible is widely used we exclude it with this generic filter.
        # A better option would be to filter based on script content basis or other marker while hunting
        ParentCommandLine|contains:
            # '{"failed":true,"msg":"Ansible requires PowerShell v3.0 or newer"}'
            - 'JwB7ACIAZgBhAGkAbABlAGQAIgA6AHQAcgB1AGUALAAiAG0AcwBnACIAOgAiAEEAbgBzAGkAYgBsAGUAIAByAGUAcQB1AGkAcgBlAHMAIABQAG8AdwBlAHIAUwBoAGUAbABsACAAdgAzAC4AMAAgAG8AcgAgAG4AZQB3AGUAcgAiAH0AJw'
            - 'cAewAiAGYAYQBpAGwAZQBkACIAOgB0AHIAdQBlACwAIgBtAHMAZwAiADoAIgBBAG4AcwBpAGIAbABlACAAcgBlAHEAdQBpAHIAZQBzACAAUABvAHcAZQByAFMAaABlAGwAbAAgAHYAMwAuADAAIABvAHIAIABuAGUAdwBlAHIAIgB9ACcA'
            - 'nAHsAIgBmAGEAaQBsAGUAZAAiADoAdAByAHUAZQAsACIAbQBzAGcAIgA6ACIAQQBuAHMAaQBiAGwAZQAgAHIAZQBxAHUAaQByAGUAcwAgAFAAbwB3AGUAcgBTAGgAZQBsAGwAIAB2ADMALgAwACAAbwByACAAbgBlAHcAZQByACIAfQAnA'
    condition: selection_img and 1 of selection_parent_* and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Unknown
level: high

high

File Decoded From Base64/Hex Via Certutil.EXE

Detects the execution of certutil with either the "decode" or "decodehex" flags to decode base64 or hex encoded files. This can be abused by attackers to decode an encoded payload before execution

status test author Florian Roth (Nextron Systems), Jonhnathan Ribeiro, oscd.community id cc9cbe82-7bc0-4ef5-bc23-bbfb83947be7

view Sigma YAML

title: File Decoded From Base64/Hex Via Certutil.EXE
id: cc9cbe82-7bc0-4ef5-bc23-bbfb83947be7
status: test
description: Detects the execution of certutil with either the "decode" or "decodehex" flags to decode base64 or hex encoded files. This can be abused by attackers to decode an encoded payload before execution
references:
    - https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/certutil
    - https://unit42.paloaltonetworks.com/new-babyshark-malware-targets-u-s-national-security-think-tanks/
    - https://news.sophos.com/en-us/2021/04/13/compromised-exchange-server-hosting-cryptojacker-targeting-other-exchange-servers/
    - https://twitter.com/JohnLaTwC/status/835149808817991680
    - https://learn.microsoft.com/en-us/archive/blogs/pki/basic-crl-checking-with-certutil
    - https://lolbas-project.github.io/lolbas/Binaries/Certutil/
author: Florian Roth (Nextron Systems), Jonhnathan Ribeiro, oscd.community
date: 2023-02-15
modified: 2025-06-04
tags:
    - attack.stealth
    - attack.t1027
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\certutil.exe'
        - OriginalFileName: 'CertUtil.exe'
    selection_cli:
        CommandLine|contains|windash:
            - '-decode ' # Decode Base64
            - '-decodehex ' # Decode Hex
    condition: all of selection_*
falsepositives:
    - Unknown
level: high
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_certutil_decode/info.yml

high

File In Suspicious Location Encoded To Base64 Via Certutil.EXE

Detects the execution of certutil with the "encode" flag to encode a file to base64 where the files are located in potentially suspicious locations

status test author Nasreddine Bencherchali (Nextron Systems) id 82a6714f-4899-4f16-9c1e-9a333544d4c3

view Sigma YAML

title: File In Suspicious Location Encoded To Base64 Via Certutil.EXE
id: 82a6714f-4899-4f16-9c1e-9a333544d4c3
related:
    - id: e62a9f0c-ca1e-46b2-85d5-a6da77f86d1a
      type: derived
status: test
description: Detects the execution of certutil with the "encode" flag to encode a file to base64 where the files are located in potentially suspicious locations
references:
    - https://www.virustotal.com/gui/file/35c22725a92d5cb1016b09421c0a6cdbfd860fd4778b3313669b057d4a131cb7/behavior
    - https://www.virustotal.com/gui/file/427616528b7dbc4a6057ac89eb174a3a90f7abcf3f34e5a359b7a910d82f7a72/behavior
    - https://www.virustotal.com/gui/file/34de4c8beded481a4084a1fd77855c3e977e8ac643e5c5842d0f15f7f9b9086f/behavior
    - https://www.virustotal.com/gui/file/4abe1395a09fda06d897a9c4eb247278c1b6cddda5d126ce5b3f4f499e3b8fa2/behavior
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-05-15
modified: 2024-03-05
tags:
    - attack.stealth
    - attack.t1027
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\certutil.exe'
        - OriginalFileName: 'CertUtil.exe'
    selection_cli:
        CommandLine|contains|windash: '-encode'
    selection_extension:
        CommandLine|contains:
            # Note: Add more suspicious locations to increase coverage
            - '\AppData\Roaming\'
            - '\Desktop\'
            - '\Local\Temp\'
            - '\PerfLogs\'
            - '\Users\Public\'
            - '\Windows\Temp\'
            - '$Recycle.Bin'
    condition: all of selection_*
falsepositives:
    - Unknown
level: high
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_certutil_encode_susp_location/info.yml

high

HackTool - CrackMapExec PowerShell Obfuscation

The CrachMapExec pentesting framework implements a PowerShell obfuscation with some static strings detected by this rule.

status test author Thomas Patzke id 6f8b3439-a203-45dc-a88b-abf57ea15ccf

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title: HackTool - CrackMapExec PowerShell Obfuscation
id: 6f8b3439-a203-45dc-a88b-abf57ea15ccf
status: test
description: The CrachMapExec pentesting framework implements a PowerShell obfuscation with some static strings detected by this rule.
references:
    - https://github.com/byt3bl33d3r/CrackMapExec
    - https://github.com/byt3bl33d3r/CrackMapExec/blob/0a49f75347b625e81ee6aa8c33d3970b5515ea9e/cme/helpers/powershell.py#L242
author: Thomas Patzke
date: 2020-05-22
modified: 2023-02-21
tags:
    - attack.execution
    - attack.stealth
    - attack.t1059.001
    - attack.t1027.005
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith:
              - '\powershell.exe'
              - '\pwsh.exe'
        - OriginalFileName:
              - 'PowerShell.EXE'
              - 'pwsh.dll'
    selection_cli:
        CommandLine|contains:
            - 'join*split'
            # Line 343ff
            - '( $ShellId[1]+$ShellId[13]+''x'')'
            - '( $PSHome[*]+$PSHOME[*]+'
            - '( $env:Public[13]+$env:Public[5]+''x'')'
            - '( $env:ComSpec[4,*,25]-Join'''')'
            - '[1,3]+''x''-Join'''')'
    condition: all of selection_*
falsepositives:
    - Unknown
level: high

high

Invoke-Obfuscation CLIP+ Launcher