135
Microsoft RPC endpoint mapper — core Windows service
Microsoft RPC Endpoint Mapper
What is port 135?
Port 135 is used by Windows for the Microsoft RPC Endpoint Mapper, which directs clients to the correct dynamic port for DCOM, WMI, Exchange, and Active Directory replication services. Historically it has been the entry point for serious worms such as Blaster and Sasser. It must be blocked at the internet perimeter and permitted only within trusted internal networks.
Quick checks
$
nc -zv example.com 135
$
nmap -p 135 example.com
$
telnet example.com 135