You are most probably logging into a domain controller which logs your computer in on a domain with security policies enabled, to bypass the proxy so that you can view all the websites, download jap from http://jap.en.softonic.com/
and then follow the installation instructions. To get the passwords of the computers running on the network you will use Cain & Abel, get it from http://www.oxid.it
and install it, enable the sniffer and sniff the network. You will see just how powerful that tool is once you have it.