Unauthorized DNS Server Response from External Host
This rule detects unauthorized DNS server responses originating from external hosts. Specifically, it looks for UDP traffic on port 53 (DNS) with a specific content signature '|84 00|' at an offset of 2 bytes and a depth of 2 bytes, which corresponds to a DNS response header indicating a standard query response. The rule uses a threshold to alert if 10 such responses are observed from the same source within 30 seconds, suggesting a potential unauthorized or malicious DNS activity.
Suricata
