Internet UDP port 111 is primarily used by the Sun RPC (Remote Procedure Call) protocol, which is a framework developed by Sun Microsystems. This protocol allows a program to make a subroutine or procedure call on a remote machine. NFS (Network File System), NIS (Network Information Service), and other services under UNIX and Linux operating systems often use this port. However, it's important to note that the use of port 111 can pose a security risk if not properly managed.
UDP port 111 is associated with the RPCbind service, which is used by NFS and NIS. In the past, hackers have exploited this port to gain unauthorized access to systems. They use port 111 to query the RPCbind service and find out what RPC services are running. Once they have this information, they can exploit vulnerabilities in those services to gain control over the system. For instance, in the late 90s, the "sadmind/IIS" worm exploited a vulnerability in the RPCbind service to propagate itself across networks. This led to widespread system compromise and data loss.
