Terminal Services uses TCP Port 3389 by default, however since it is well known port that Terminal Services uses this port it can be a target for the attack by the intruders.
You can change the port no. by editing the following registry entry:
- Key Name: HKEY_LOCAL_MACHINE\System\CurrentConrolSet\Control\TerminalServer\WinStations\RDP-Tcp
- Entry Name: Port Number
- Type: REG_DWORD
- Data: 3389(d) or d3d(h)