closing port 6881

Hello,

since today we got a lot of

11:38:59 Default DROP Bittorrent 91.240.97.1 : 37666 → ***x : 6881

every second new drops comes into the log.

so is it possible to close, deactivate this port 6881? bittorrent is not allowed here. we doesnt need the port 6881 for any other software.

thx

more informations:
until no 779 violations
Top drop destinations services:
1
udp/6881 *** WAN (Address) 47 532 Packets 52.58%
2
tcp/6881 *** WAN (Address) 24 514 Packets 27.12%

just from today.. how can i block this bittorrent connections from outside on our wan address?

different ip´s