Internet-Security.com TCP port 635 details

NFS mount daemon (rpc.mountd) has historically been exposed on TCP port 635 on many Unix/Linux systems, often listed as "mount" in /etc/services and mapped there by portmapper (e.g., older Red Hat Linux and some Solaris/IRIX configurations).
Real-world example: nfs-utils’ rpc.mountd on older Red Hat Linux 6/7-era servers was commonly reachable on TCP 635 for NFS client mount requests.
Some Solaris deployments also exposed rpc.mountd on TCP 635, depending on portmapper assignments and admin configuration.
Security note: rpc.mountd on port 635 was a frequent target of early-2000s remote exploits (buffer overflows/format-string bugs) that allowed root compromise on vulnerable NFS servers.

TCP 635