TCP Port 513 – login
About TCP Port 513
Port 513 is registered with the Internet Assigned Numbers Authority (IANA) for login. The IANA description reads: ‘remote login a la telnet; automatic authentication performed based on priviledged port numbers and distributed data bases which identify "authentication domains"’. This port appears in 8 IDS rules and does not have notable malware activity indicators in our data.
IDS Rule References
8 IDS / security rules reference TCP port 513. 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 4): attempted-admin (3), bad-unknown (2), unsuccessful-user (2), attempted-user (1).
Sample rule descriptions for TCP port 513:
- PROTOCOL-SERVICES rlogin LinuxNIS
- PROTOCOL-SERVICES rlogin bin
- PROTOCOL-SERVICES rlogin echo++
- PROTOCOL-SERVICES Unix rlogin froot parameter root access attempt
- PROTOCOL-SERVICES rlogin login failure
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).