What software/application do I need to monitor internet usage of computers in my network to see sites they are browsing?
closed as not constructive by Shane Madden, Jed Daniels, Lucas Kauffman, Khaled, Zoredache Apr 19 '12 at 0:40
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You'll need some form of intelligence in your gateway. You can have monitoring solutions be in-line with traffic or some form of side-band monitoring. I suggest starting with researching Squid as your gateway device and then looking at its many plugins to enable more thorough internet monitoring.
I recommend the appliance approach.
If the budget allows, the Barracuda Web Filter is a good solution to monitor and manage internet activity. It has comprehensive reporting, granular configurations and is easy for non-technical users (policy-makers) to manage.