Connection to Commonly Abused Free SSL Certificate Providersedit

Identifies unusual processes connecting to domains using known free SSL certificates. Adversaries may employ a known encryption algorithm to conceal command and control traffic.

Rule type: eql

Rule indices:

  • winlogbeat-*
  • logs-windows.*

Severity: low

Risk score: 21

Runs every: 5m

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

Maximum alerts per execution: 100

References: None


  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Command and Control

Version: 4

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guideedit

## 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 queryedit

network where network.protocol == "dns" and
  /* Add new free SSL certificate provider domains here */ : ("*", "*", "*", "*") and

  /* Native Windows process paths that are unlikely to have network connections to domains secured using free SSL certificates */
  process.executable : ("C:\\Windows\\System32\\*.exe",
		          "C:\\Windows\\notepad.exe") and

  /* Insert noisy false positives here */
  not : ("svchost.exe", "MicrosoftEdge*.exe", "msedge.exe")