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Elastic Docs ›Elastic Security Solution [8.2] ›Detections and alerts ›Prebuilt rule reference

Creation of Hidden Files and Directories

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Creation of Hidden Files and Directories

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Users can mark specific files as hidden simply by putting a "." as the first character in the file or folder name. Adversaries can use this to their advantage to hide files and folders on the system for persistence and defense evasion. This rule looks for hidden files or folders in common writable directories.

Rule type: eql

Rule indices:

  • auditbeat-*
  • logs-endpoint.events.*

Severity: medium

Risk score: 47

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 33

Tags:

  • Elastic
  • Host
  • Linux
  • Threat Detection
  • Defense Evasion

Version: 8 (version history)

Added (Elastic Stack release): 7.9.0

Last modified (Elastic Stack release): 8.2.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positives

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Certain tools may create hidden temporary files or directories upon installation or as part of their normal behavior. These events can be filtered by the process arguments, username, or process name values.

Investigation guide

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## Config

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define `event.ingested` and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.

Rule query

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process where event.type in ("start", "process_started") and
process.working_directory in ("/tmp", "/var/tmp", "/dev/shm") and
process.args regex~ """\.[a-z0-9_\-][a-z0-9_\-\.]{1,254}""" and not
process.name in ("ls", "find")

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 8 (8.2.0 release)
  • Formatting only
Version 7 (7.14.0 release)

  • Updated query, changed from:

    event.category:process AND event.type:(start or process_started) AND
process.working_directory:("/tmp" or "/var/tmp" or "/dev/shm") AND
process.args:/\.[a-zA-Z0-9_\-][a-zA-Z0-9_\-\.]{1,254}/ AND NOT
process.name:(ls or find)
Version 6 (7.12.0 release)
  • Formatting only
Version 5 (7.11.2 release)
  • Formatting only
Version 4 (7.11.0 release)
  • Formatting only
Version 3 (7.10.0 release)
  • Formatting only
Version 2 (7.9.1 release)
  • Formatting only
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