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Elastic Docs ›SIEM Guide [7.8] ›Detections (beta) ›Prebuilt rule reference

Web Application Suspicious Activity: No User Agent

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Web Application Suspicious Activity: No User Agent

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A request to a web application server contained no identifying user agent string.

Rule type: query

Rule indices:

  • apm--transaction

Severity: medium

Risk score: 47

Runs every: 5 minutes

Searches indices from: now-6m (Date Math format, see also Additional look-back time)

Maximum signals per execution: 100

References:

Tags:

  • APM
  • Elastic

Version: 2 (version history)

Added (Elastic Stack release): 7.6.0

Last modified (Elastic Stack release): 7.7.0

Potential false positives

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Some normal applications and scripts may contain no user agent. Most legitimate web requests from the Internet contain a user agent string. Requests from web browsers almost always contain a user agent string. If the source is unexpected, the user unauthorized, or the request unusual, these may indicate suspicious or malicious activity.

Rule query

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url.path:*

Rule filters

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{
    "$state": {
        "store": "appState"
    },
    "exists": {
        "field": "user_agent.original"
    },
    "meta": {
        "disabled": false,
        "indexRefName": "kibanaSavedObjectMeta.searchSourceJSON.filter[0].meta.index",
        "key": "user_agent.original",
        "negate": true,
        "type": "exists",
        "value": "exists"
    }
}

Rule version history

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Version 2 (7.7.0 release)

Updated query, changed from: 

url.path: *
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