The patch that comes with winmx if you downloaded it from patch.winmxconex.com comes with its own blocking and filtering solution. It does over two methods.
1.The patch when running primary monitors what secondary are trying to connect. If any ip on this page
https://www.winmxworld.com/files/block_list.txt trys to connect to your winmx it blocks it and drops it. If you have the patch from winmxconex you will see on update bar at the top that says <FSR=?? BC=??> The BC is blocked connections ie the nasty people on that page and goes up every time it blocks one of them..
2. The second stage is search result filtering. Not everyone on winmx is using the DLL. Either threw being misinformed or just don't know about its capabilities and think well im connected an so what. But primary's are out their that have let the flooders connect to them. Now once they are connected they flood winmx with loads of fake file names so that when you do a search you get 1000 results but only maybe 10 of them are real. Making your life to find these 10 a royal pain in the arse. and making you want to give up(then they have won). But the patch we support intercepts the search details when you do a search and using the ip's from the block list posted above filters out the fake files using a clever process which we could discuss if you are a coder or magic if you happy to trust what i say and only gives you the 10 results out of the 1000. This process is shown to you again in the update bar as FSR=?? or filtered search results. This goes up every time it filters fakes from one of your searches
To answer you question as to what from who the only person who can do this is your ISP. Winmx considering when it was made was at the forefront of encryption long before limewire or bittorrent even thought about this. So 90% of what you do over the winmx network is fully encrypted. Its only the actual transfer between user to user that is unencrypted but the process of finding that user is fully encrypted and they are unable to monitor it.