- no such thing as blocking FTP function - it's just more 1s and 0s through TCP.
Actually, that's not true. it's fairly easy to find the connection packets for FTP, because the protocol is quite verbose. There are boxes now that only do packet inspections as traffic goes through them, so they could easily silently drop FTP connection packets regardless of what port they're on.
A place I used to work for did this with P2P traffic, except instead of dropping the packets altogether, it modified one of the fields in the header so that it looked like there was a lot of network congestion and the speed was dropped to a 14.4 kbps modem.