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Suspicious File Changes Activity Detected

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Suspicious File Changes Activity Detected

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Ransomware is a type of malware that encrypts a victim’s files or systems and demands payment (usually in cryptocurrency) in exchange for the decryption key. One important indicator of a ransomware attack is the mass encryption of the file system, after which a new file extension is added to the file. This rule identifies a sequence of 50 file extension rename events by the same process in a timespan of 1 second.

Rule type: eql

Rule indices:

  • logs-endpoint.events.*

Severity: high

Risk score: 73

Runs every: 5m

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

Maximum alerts per execution: 100

References: None

Tags:

  • Domain: Endpoint
  • OS: Linux
  • Use Case: Threat Detection
  • Tactic: Impact

Version: 2

Rule authors:

  • Elastic

Rule license: Elastic License v2

Rule query

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sequence by host.id, process.entity_id, file.extension with maxspan=1s
[ file where host.os.type == "linux" and event.type == "change" and
  event.action == "rename" and file.extension != "" ] with runs=50 | tail 1

Framework: MITRE ATT&CKTM

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