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Suspicious Data Encryption via OpenSSL Utility

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Suspicious Data Encryption via OpenSSL Utility

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Identifies when the openssl command-line utility is used to encrypt multiple files on a host within a short time window. Adversaries may encrypt data on a single or multiple systems in order to disrupt the availability of their target’s data and may attempt to hold the organization’s data to ransom for the purposes of extortion.

Rule type: eql

Rule indices:

  • logs-endpoint.events.*

Severity: medium

Risk score: 47

Runs every: 5m

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

Maximum alerts per execution: 100

References:

Tags:

  • Domain: Endpoint
  • OS: Linux
  • Use Case: Threat Detection
  • Tactic: Impact
  • Data Source: Elastic Defend

Version: 4

Rule authors:

  • Elastic

Rule license: Elastic License v2

Rule query

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sequence by host.id, user.name, process.parent.entity_id with maxspan=5s
  [ process where host.os.type == "linux" and event.action == "exec" and
    process.name == "openssl" and process.parent.name : ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish", "perl*", "php*", "python*", "xargs") and
    process.args == "-in" and process.args == "-out" and
    process.args in ("-k", "-K", "-kfile", "-pass", "-iv", "-md") and
    /* excluding base64 encoding options and including encryption password or key params */
    not process.args in ("-d", "-a", "-A", "-base64", "-none", "-nosalt") ] with runs=10

Framework: MITRE ATT&CKTM

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