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I got a 3G modem and a sim card. I have a 100MB day limit and although I mostly use firefox and thunderbird and I take care, sometimes it seems that something is using bandwidth but i do not know exactly what program.

How could i tell OS X that only firefox and thunderbird can connect to the internet? so I avoid checking if the rest of the applications connect to the inrenet

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do you mean that it cat not be implemented using shell programming or apple script? – asdf Dec 24 '09 at 18:06
Dupe of… – ceejayoz Dec 24 '09 at 18:20

OS X has an IPFW firewall, so you might be able to configure this to your needs.

A more user friendly solution would be Little Snitch, which has a free version (prompts every three hours) if you don't want to buy it.

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Little Snitch can do it.

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To get a list of processes that have open connections, you can use:

sudo lsof | grep -i tcp | grep ESTABLISHED
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