So not sure if people are aware of his buit there's a fan patch for this game which lets you view servers from your server browser without LAN (using Internet) and it really works quite well:
https://github.com/sergeii/swat-patches/tree/master/swat4stats-masterserver#master-server-patch

I tried it and it seems to work flawlessly. AFAIK this is legit, but if it isn't, please let me know.