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Unusual Web User Agent

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Unusual Web User Agent

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A machine learning job detected a rare and unusual user agent indicating web browsing activity by an unusual process other than a web browser. This can be due to persistence, command-and-control, or exfiltration activity. Uncommon user agents coming from remote sources to local destinations are often the result of scanners, bots, and web scrapers, which are part of common Internet background traffic. Much of this is noise, but more targeted attacks on websites using tools like Burp or SQLmap can sometimes be discovered by spotting uncommon user agents. Uncommon user agents in traffic from local sources to remote destinations can be any number of things, including harmless programs like weather monitoring or stock-trading programs. However, uncommon user agents from local sources can also be due to malware or scanning activity.

Rule type: machine_learning

Machine learning job: packetbeat_rare_user_agent

Machine learning anomaly threshold: 50

Severity: low

Risk score: 21

Runs every: 15 minutes

Searches indices from: now-45m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://www.elastic.co/guide/en/security/current/prebuilt-ml-jobs.html

Tags:

Elastic
Network
Threat Detection
ML
Command and Control

Version: 100 (version history)

Added (Elastic Stack release): 7.7.0

Last modified (Elastic Stack release): 8.5.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positives

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Web activity that is uncommon, like security scans, may trigger this alert and may need to be excluded. A new or rarely used program that calls web services may trigger this alert. ==== Threat mapping

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Command and Control
- ID: TA0011
- Reference URL: https://attack.mitre.org/tactics/TA0011/
Technique:
- Name: Application Layer Protocol
- ID: T1071
- Reference URL: https://attack.mitre.org/techniques/T1071/

Rule version history

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Version 100 (8.5.0 release)

Formatting only

Version 5 (8.4.0 release)

Formatting only

Version 4 (7.12.0 release)

Formatting only

Version 3 (7.10.0 release)

Formatting only

Version 2 (7.9.0 release)

Formatting only

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