Nasreddine Bencherchali
598d29f811
chore: change tags, date, modified fields to comply with v2 of the Sigma spec. chore: update the related type from `obsoletes` to `obsolete`. chore: update local json schema to the latest version.
51 lines
2.5 KiB
YAML
51 lines
2.5 KiB
YAML
title: Suspicious User Agent
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id: 7195a772-4b3f-43a4-a210-6a003d65caa1
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status: test
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description: Detects suspicious malformed user agent strings in proxy logs
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references:
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- https://github.com/fastly/waf_testbed/blob/8bfc406551f3045e418cbaad7596cff8da331dfc/templates/default/scanners-user-agents.data.erb
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author: Florian Roth (Nextron Systems)
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date: 2017-07-08
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modified: 2022-10-31
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tags:
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- attack.command-and-control
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- attack.t1071.001
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logsource:
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category: proxy
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detection:
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selection1:
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c-useragent|startswith:
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- 'user-agent' # User-Agent: User-Agent:
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- 'Mozilla/3.0 '
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- 'Mozilla/2.0 '
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- 'Mozilla/1.0 '
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- 'Mozilla ' # missing slash
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- ' Mozilla/' # leading space
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- 'Mozila/' # single 'l'
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- 'Mozilla/4.0 (compatible; MSIE 6.0; MS Web Services Client Protocol' # https://twitter.com/NtSetDefault/status/1303643299509567488
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selection2:
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c-useragent|contains:
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- ' (compatible;MSIE ' # typical typo - missing space
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- '.0;Windows NT ' # typical typo - missing space
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- 'loader' # https://twitter.com/securityonion/status/1522614635152744453?s=20&t=gHyPTSq5A27EqKwrCd9ohg
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selection3:
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c-useragent:
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- '_'
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- 'CertUtil URL Agent' # https://twitter.com/stvemillertime/status/985150675527974912
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- 'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:60.0)' # CobaltStrike Beacon https://unit42.paloaltonetworks.com/tracking-oceanlotus-new-downloader-kerrdown/
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- 'Mozilla/5.0 (Windows NT 6.3; WOW64; rv:28.0) Gecko/20100101 Firefox/28.0' # used by APT28 malware https://threatvector.cylance.com/en_us/home/inside-the-apt28-dll-backdoor-blitz.html
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- 'HTTPS' # https://twitter.com/stvemillertime/status/1204437531632250880
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- 'Erbium-UA-4ce7c27cb4be9d32e333bf032c88235a' # https://www.cyfirma.com/outofband/erbium-stealer-malware-report
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- 'x' # Use by Racoon Stealer but could be something else
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- 'xxx' # Use by Racoon Stealer but could be something else
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falsepositives:
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- c-useragent: 'Mozilla/3.0 * Acrobat *' # Acrobat with linked content
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- cs-host|endswith: # Adobe product traffic, example: Mozilla/3.0 (compatible; Adobe Synchronizer 10.12.20000)
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- '.acrobat.com'
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- '.adobe.com'
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- '.adobe.io'
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condition: 1 of selection* and not falsepositives
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falsepositives:
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- Unknown
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level: high
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