Goal

This rule detects if your Apache or NGINX web servers are being scanned for the log4j vulnerability. The initial vulnerability was identified as CVE-2021-44228.

Strategy

This signal evaluated that jndi:(ldap OR rmi OR dns) has been detected in the HTTP header fields user agent and referrer or referer.

Triage and response

1. Ensure you servers have the most recent version of log4j installed.
2. Check if the Base64 was detected in an http.user_agent or http.referrer rule was also triggered and follow the Triage and response steps in that rule.

Note: Datadog’s The Monitor blog has an article published about “The Log4j Logshell vulnerability: Overview, detection, and remediation”.