{"id":"21e44d78-95e7-421b-a464-ffd8395659c4","title":"HTTP Request With Empty User Agent","description":"Detects a potentially suspicious empty user agent strings in proxy log.\nCould potentially indicate an uncommon request method.\n","author":"Florian Roth (Nextron Systems)","status":"test","level":"medium","date":"2017-07-08","modified":"2021-11-27","tags":["attack.command-and-control","attack.t1071.001"],"technique_ids":["T1071.001"],"logsource":{"category":"proxy"},"falsepositives":["Unknown"],"references":["https://twitter.com/Carlos_Perez/status/883455096645931008"],"source_path":"rules/web/proxy_generic/proxy_ua_empty.yml","source_sha256":"ea65359c4a8b22fe8154f8f7a22e5b71eaaa06bd47ce4fa1f35e1834db81f6f9","source_url":"https://github.com/anpa1200/sigma/blob/b249e9683190cffdcaf188ccbfb90bf4759844e1/rules/web/proxy_generic/proxy_ua_empty.yml","license":"Detection Rule License 1.1","license_url":"https://github.com/SigmaHQ/Detection-Rule-License/blob/main/LICENSE.Detection.Rules.md","yaml":"title: HTTP Request With Empty User Agent\nid: 21e44d78-95e7-421b-a464-ffd8395659c4\nstatus: test\ndescription: |\n    Detects a potentially suspicious empty user agent strings in proxy log.\n    Could potentially indicate an uncommon request method.\nreferences:\n    - https://twitter.com/Carlos_Perez/status/883455096645931008\nauthor: Florian Roth (Nextron Systems)\ndate: 2017-07-08\nmodified: 2021-11-27\ntags:\n    - attack.command-and-control\n    - attack.t1071.001\nlogsource:\n    category: proxy\ndetection:\n    selection:\n      # Empty string - as used by Powershell's (New-Object Net.WebClient).DownloadString\n        c-useragent: ''\n    condition: selection\nfalsepositives:\n    - Unknown\nlevel: medium\n","validation":"yaml_parsed_not_backend_compiled_or_live_validated","techniques":[{"key":"enterprise/T1071.001","id":"T1071.001","name":"Web Protocols","page":"techniques/enterprise/T1071.001/"}],"data_path":"data/detection-rules/21e44d78-95e7-421b-a464-ffd8395659c4.json","kind":"sigma"}