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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?

share|improve this question
If it is some sort of proxy then you might be able to bypass/test it with telnet 80 and typing something like HTTP/1.1 [Return]). – Hennes Jan 25 '13 at 13:32
How you check is you uninstall all the programs you suspect might be the problem until you find the reason for this behavior or at the very least do exactly that then report back with the information you found. As for the reason you have software install on your Apple computer that is causing this. – Ramhound Jan 25 '13 at 14:46

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