I am working on a MacBook running 10.8.2, and when I make a connection to port 80 to a server that doesn't respond (because of network issues, typically), something on the machine causes the connect to return success -- and then closes the connection after a few seconds. Happens even with plain telnet, doesn't happen for port 443.
Makes it more fun to try and diagnose network problems.
I have seen similar behaviour with anti-virus email scanners (on Windows) which is why I suspect some sort of security product is doing it.
Sophos? Cisco AnyConnect (even though no VPN is established)? Old Cisco VPN client?
How to check? How to disable?