I need to prove the need we have to install SSL certificates in our webservers.
For that I've been requested to try obtaining sample credentials (in lab enviroment) during a http authentication process.
How can I do this?
Use a packet capture tool like Wireshark to search for the password string as it passes over the network. Basically, wireshark makes a copy of all the network packets it can see from the computer it is installed on. You then use various tools and filters to search those captured packets for data you're interested in.
Step by step instructions can be easily found online (here for example), but are a bit too involved to reproduce here.