Website content filtering software

Hello,

I am trying to help a client look for a desktop application that can stop employees from accessing social sites such as “Facebook” “Reddit” etc… The approved software must address the following:

1.) Work with both Firefox and I.E.
2.) Allow for Https: pass-through for internal servers – not just www. sites
3.) They only want to lock down specific workstations not the whole environment.
4.) Allow corporate approved proxy only

Thoughts???