Internet-Security.com UDP port 5500 details

RSA SecurID Authentication Manager (formerly ACE/Server) uses UDP port 5500 (IANA service name: securid) for communication between SecurID agents and the authentication server.
Example deployments include RSA SecurID agents integrated with VPN gateways (e.g., Cisco ASA/AnyConnect when using the RSA agent), web servers (e.g., Apache/IIS with RSA agents), and PAM/SSH agents on Unix/Linux, which send authentication requests to the RSA server over UDP/5500.
Administrators typically allow inbound UDP/5500 to the RSA Authentication Manager server and permit return traffic to the agent’s ephemeral port.
Beyond RSA SecurID, there are no widely recognized, documented applications that commonly use UDP/5500.

UDP 5500