UDP Port 53 – DNS (Domain Name System)
About UDP Port 53
Port 53 carries the IANA assignment for domain. The IANA description reads: ‘Domain Name Server’. This port is referenced in 61 IDS rules and exhibits high malware activity in monitored traffic.
IDS Rule References
61 IDS / security rules reference UDP port 53. Treat that number as context, not a danger score. Many detection rules are written against groups of ports rather than one service, web ports especially, so common web alternate ports inherit large counts while genuinely sensitive services can show few rules or none. Presence in IDS rules does not mean traffic on this port is malicious.
Rule categories (top 6): trojan-activity (27), attempted-recon (8), attempted-user (7), bad-unknown (5), attempted-dos (5), attempted-admin (3).
Sample rule descriptions for UDP port 53:
- PROTOCOL-DNS SPOOF query response PTR with TTL of 1 min. and no authority
- PROTOCOL-DNS SPOOF query response with TTL of 1 min. and no authority
- PROTOCOL-DNS named authors attempt
- SERVER-OTHER Bind Buffer Overflow named tsig overflow attempt
- PROTOCOL-DNS named version attempt
Malware Rule References
A large share of the IDS rules that reference this port are malware related.
32 of the 61 IDS rules that reference UDP port 53 are malware related. That describes detection coverage across the whole internet, not anything about your machine or your network.
Families observed (top 8): Dyre (6), UDPOS (4), Cobalt Strike (3), FrameworkPOS (2), Hyteod.acox (2), Onimiki (2), Tinba (2), ZeroAccess (2), and 9 more families.
Data Sources
This information is compiled from: IANA Service Name and Transport Protocol Port Number Registry, Emerging Threats Open Ruleset (BSD 2-Clause / GPLv2 per SID range), Snort Community Rules (GPLv2), and MITRE ATT&CK (Apache 2.0).