Connection to Commonly Abused Free SSL Certificate Providers

Last updated 5 months ago on 2025-03-20
Created 5 years ago on 2020-11-04

About

Identifies unusual processes connecting to domains using known free SSL certificates. Adversaries may employ a known encryption algorithm to conceal command and control traffic.
Tags
Domain: EndpointOS: WindowsUse Case: Threat DetectionTactic: Command and ControlData Source: Elastic DefendData Source: SysmonLanguage: eql
Severity
low
Risk Score
21
MITRE ATT&CK™

Command and Control (TA0011)(opens in a new tab or window)

License
Elastic License v2(opens in a new tab or window)

Definition

Rule Type
Event Correlation Rule
Integration Pack
Prebuilt Security Detection Rules
Index Patterns
winlogbeat-*logs-endpoint.events.network-*logs-windows.sysmon_operational-*
Related Integrations

endpoint(opens in a new tab or window)

windows(opens in a new tab or window)

Query
network where host.os.type == "windows" and network.protocol == "dns" and
  /* Add new free SSL certificate provider domains here */
  dns.question.name : ("*letsencrypt.org", "*.sslforfree.com", "*.zerossl.com", "*.freessl.org") 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\\System\\*.exe",
	                  "C:\\Windows\\SysWOW64\\*.exe",
		          "C:\\Windows\\Microsoft.NET\\Framework*\\*.exe",
		          "C:\\Windows\\explorer.exe",
		          "C:\\Windows\\notepad.exe") and

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

Install detection rules in Elastic Security

Detect Connection to Commonly Abused Free SSL Certificate Providers in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(opens in a new tab or window).