Network attacks blocked... *from* FTP Mount!

Does anyone have any idea why Kaspersky's firewall occasionally (but regularly) reports that it has blocked a network attack, when I am using FTP Mount on OS4 (over a local network) to access a FileZilla FTP server on my PC?

It has done this for at least a year or two. The IP address is clearly my Amiga, and the port numbers range from about 50000 to 50099 (seemingly at random). It happens about once per minute when heavily using FTP Mount (say to compare files).

The FileZila FTP server listens on port 21, of course.

EDIT: From browsing FileZilla's settings, I just discovered that "Passive mode settings" has "Use custom port range" set to "50000 to 50100"... So the next question is, how do I stop it the problem? Would unticking "use custom port range" be sufficient & safe?

It's probably PASV mode, is it the 'QUICK' tooltype in FTPMount? There's one which uses a spread of ports which is likely the reason.

@Chris
From browsing FileZilla's settings, I just discovered that "Passive mode settings" has "Use custom port range" set to "50000 to 50100"... So the next question is, how do I stop it the problem? Would unticking "use custom port range" be sufficient & safe?

I never understood what "passive" mode is.

Possibly, and if you add the SLOW tooltype in your connection in FTPMount that will stop it spamming the server.

Passive is when the client and the server start talking on port 21 but then the client is passive and the server talks to him on a port from its port range (50000 to 50100 in your case).
The server chooses a communication port at random from the defined range.
My guess is that Kaspersky warns you when the server chooses a port which is not opened in its settings. You need to change the settings to open all ports of the range.