{"id":"fdb62a13-9a81-4e5c-a38f-ea93a16f6d7c","title":"PowerShell Base64 Encoded FromBase64String Cmdlet","description":"Detects usage of a base64 encoded \"FromBase64String\" cmdlet in a process command line","author":"Florian Roth (Nextron Systems)","status":"test","level":"high","date":"2019-08-24","modified":"2023-04-06","tags":["attack.stealth","attack.t1140","attack.execution","attack.t1059.001"],"technique_ids":["T1059.001","T1140"],"logsource":{"category":"process_creation","product":"windows"},"falsepositives":["Unknown"],"references":["Internal Research"],"source_path":"rules/windows/process_creation/proc_creation_win_powershell_base64_frombase64string.yml","source_sha256":"b1945e32d381f1293be6d91e44e4472c9a208f7da9338b3cebda2901176a31a9","source_url":"https://github.com/anpa1200/sigma/blob/b249e9683190cffdcaf188ccbfb90bf4759844e1/rules/windows/process_creation/proc_creation_win_powershell_base64_frombase64string.yml","license":"Detection Rule License 1.1","license_url":"https://github.com/SigmaHQ/Detection-Rule-License/blob/main/LICENSE.Detection.Rules.md","yaml":"title: PowerShell Base64 Encoded FromBase64String Cmdlet\nid: fdb62a13-9a81-4e5c-a38f-ea93a16f6d7c\nstatus: test\ndescription: Detects usage of a base64 encoded \"FromBase64String\" cmdlet in a process command line\nreferences:\n    - Internal Research\nauthor: Florian Roth (Nextron Systems)\ndate: 2019-08-24\nmodified: 2023-04-06\ntags:\n    - attack.stealth\n    - attack.t1140\n    - attack.execution\n    - attack.t1059.001\nlogsource:\n    category: process_creation\n    product: windows\ndetection:\n    selection:\n        - CommandLine|base64offset|contains: '::FromBase64String'\n        # UTF-16 LE\n        - CommandLine|contains:\n              - 'OgA6AEYAcgBvAG0AQgBhAHMAZQA2ADQAUwB0AHIAaQBuAGcA'\n              - 'oAOgBGAHIAbwBtAEIAYQBzAGUANgA0AFMAdAByAGkAbgBnA'\n              - '6ADoARgByAG8AbQBCAGEAcwBlADYANABTAHQAcgBpAG4AZw'\n    condition: selection\nfalsepositives:\n    - Unknown\nlevel: high\n","validation":"yaml_parsed_not_backend_compiled_or_live_validated","techniques":[{"key":"enterprise/T1059.001","id":"T1059.001","name":"PowerShell","page":"techniques/enterprise/T1059.001/"},{"key":"enterprise/T1140","id":"T1140","name":"Deobfuscate/Decode Files or Information","page":"techniques/enterprise/T1140/"}],"data_path":"data/detection-rules/fdb62a13-9a81-4e5c-a38f-ea93a16f6d7c.json","kind":"sigma"}