If a file is send to a server with SendNetworkFile(), all other incoming data is blocked until the file is received. There is no way to cancel the receiving of the file, i have to save the file on my HDD or the server won't work any more. If a program doesn't checks the #PB_Network_File - Event, that's an easy way to crash the server.
There should be a command like BlockNetworkFile() to block Files, or a command to disable the receiving of files generally.