If you're trying to use a socks server with Internet Explorer , Firefox, Opera or Safari everything will work just fine, except for authentication.
From my point of view this is a big problem. Who in the world would leave such a proxy server unprotected? Yeah of course you can always limit access to a proxy server based on ip address, but in some cases ( see NAT ) this is just not going to work.
Internet explorer supports only the socks4 protocol which doesn't even support full password authentication ( only username and it defaults to the current logged in username ) .
Firefox supports socks5 but no authentication mechanism so supporting socks5 is pretty much useless. I think I saw some ticket in bugzilla about this but no one managed to commit a fix yet.
Opera doesn't even support socks protocol but I thought I should mention all major browsers
Safari supports SOCKS5 and even allows you to set a username and password to access the SOCKS server but it does not use them.
I tried Konqueror, but I was unable to specify the Socks server, I guess this is because it was not compiled with a socks library. Has anyone had any success with Konqueror and Socks ?