Hello,
I have not provided the filter because, as explained,
it is the default one that comes with Plesk named "plesk-proftpd".
Here is the filter :
[plesk-proftpd]
enabled = true
filter = proftpd
action = iptables-multiport[name="plesk-proftpd", port="ftp,ftp-data,ftps,ftps-data"]
logpath =...