Query: alert when Detects suspicious malformed user agent strings in proxy logs
Matching passage: Sigma rule: Detects suspicious malformed user agent strings in proxy logs. Logsource: proxy. Rule: title: Suspicious User Agent id: 7195a772-4b3f-43a4-a210-6a003d65caa1 status: test description: Detects suspicious malformed user agent strings in proxy logs references: - https://github.com/fastly/waf_testbed/blob/8bfc406551f3045e418cbaad7596cff8da331dfc/templates/default/scanners-user-agents.data.erb author: Florian Roth (Nextron Systems) date: 2017-07-08 modified: 2022-10-31 tags: - attack.command-and-control - attack.t1071.001 logsource: category: proxy detection: selection1: c-useragent|startswith: - user-agent - 'Mozilla/3.0 ' - 'Mozilla/2.0 ' - 'Mozilla/1.0 ' - 'Mozilla ' - ' Mozilla/' - Mozila/ - Mozilla/4.0 (compatible; MSIE 6.0; MS Web Services Client Protocol selection2: c-useragent|contains: - ' (compatible;MSIE ' - '.0;Windows NT ' - loader selection3: c-useragent: - _ - CertUtil URL Agent - Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:60.0) - Mozilla/5.0 (Windows NT 6.3; WOW64; rv:28.0) Gecko/20100101 Firefox/28.0 - HTTPS - Erbium-UA-4ce7c27cb4be9d32e333bf032c88235a - x - xxx falsepositives: - c-useragent: Mozilla/3.0 * Acrobat * - cs-host|endswith: - .acrobat.com - .adobe.com - .adobe.io condition: 1 of selection* and not falsepositives falsepositives: - Unknown level: high
Near-miss passage: Sigma rule: Detects changing the PowerShell script execution policy to a potentially insecure level using the "-ExecutionPolicy" fla. Logsource: windows / process_creation. Rule: title: Change PowerShell Policies to an Insecure Level id: 87e3c4e8-a6a8-4ad9-bb4f-46e7ff99a180 related: - id: cf2e938e-9a3e-4fe8-a347-411642b28a9f type: similar - id: 61d0475c-173f-4844-86f7-f3eebae1c66b type: similar - id: fad91067-08c5-4d1a-8d8c-d96a21b37814 type: similar status: test description: Detects changing the PowerShell script execution policy to a potentially insecure level using the "-ExecutionPolicy" flag. references: - https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.security/set-executionpolicy?view=powershell-7.4 - https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_execution_policies?view=powershell-7.4 - https://adsecurity.org/?p=2604 - https://thedfirreport.com/2021/11/01/from-zero-to-domain-admin/ author: frack113 date: 2021-11-01 modified: 2025-10-07 tags: - attack.execution - attack.t1059.001 logsource: product: windows category: process_creation detection: selection_img: - OriginalFileName: - powershell_ise.exe - PowerShell.EXE - pwsh.dll - Image|endswith: - \powershell_ise.exe - \powershell.exe - \pwsh.exe selection_option: CommandLine|contains: - '-executionpolicy ' - ' -ep ' - ' -exec ' selection_level: CommandLine|contains: - Bypass - Unrestricted filter_main_powershell_core: ParentImage: - C:\Windows\SysWOW64\msiexec.exe - C:\Windows\System32\msiexec.exe CommandLine|contains: - -NoProfile -ExecutionPolicy Bypass -File "C:\Program Files\PowerShell\7\ - -NoProfile -ExecutionPolicy Bypass -File "C:\Program Files (x86)\PowerShell\7\ filter_optional_avast: ParentImage|contains: - C:\Program Files\Avast Software\Avast\ - C:\Program Files (x86)\Avast Software\Avast\ - \instup.exe CommandLine|contains: - -ExecutionPolicy ByPass -File "C:\Program Files\Avast Software\Avast - -ExecutionPolicy ByPass -File "C:\Program Files (x86)\Avast Software\Avast\ condition: all of selection_* and not 1 of filter_main_* and not 1 of filter_optional_* falsepositives: - Administrator scripts level: medium