I just built the website and then made the security scan by Acunetix Web Vulnerability Scanner which identified some hole in my website: "User credentials are not encrypted when they are transmitted". I guess that it means that someone who is able to monitor my website is able to capture someone's else username as well as password.

I would like to check this issue myself. Can you recommend me which tools I have to use in order to check this issue?!

I would like to check from a different computer, run some tools, and then log in with my personal computer in order to see if I can capture the credentials or not?!