Effective Incident Response Team, The

Appendix E. Well-Known Port Numbers

A listing of port numbers can be a useful tool for an incident response team when responding to an incident or reviewing audit logs. The port numbers available on computer systems range from 0 through 65535, and can be divided into three main groups:

• Well-known ports: 0 through 1023

• Registered ports: 1024 through 49151

• Dynamic and/or private ports: 49152 through 65535^[1]

  ^[1] http://www.iana.org/assignments/port-numbers.

“The Well Known Ports are assigned by the InterNet Assigned Numbers Authority (IANA) and on most systems can only be used by system (or root) processes or by programs executed by privileged users.”^[2] A complete listing of the port numbers and their assigned usage can be obtained from the IANA ...