UDP Port 4500 – ipsec-nat-t

About UDP Port 4500

Port 4500 is registered with the Internet Assigned Numbers Authority (IANA) for ipsec-nat-t. The IANA description reads: ‘IPsec NAT-Traversal’. This port appears in 4 IDS rules and does not have notable malware activity indicators in our data.

IDS Rule References

4 IDS / security rules reference UDP port 4500. 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 2): attempted-recon (3), attempted-user (1).

Sample rule descriptions for UDP port 4500:

• SERVER-OTHER Cisco IOS Group-Prime memory disclosure exfiltration attempt
• SERVER-OTHER Cisco IOS Group-Prime MD5 memory disclosure attempt
• SERVER-OTHER Cisco IOS Group-Prime SHA memory disclosure attempt
• ET EXPLOIT IKEv2 Invalid Fragmented IKE_AUTH (CVE-2026-33824)

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), and Snort Community Rules (GPLv2).