I’ll definately talk more about the Burp Suite later as it’s excellent for testing anything web-based.
Paros labels itself as MITM Proxy + Spider + Scanner plus anything else you want it to be, it is a pretty neat piece of software.
It’s particularly useful for testing web applications and things such as insecure sessions.
Paros is free of charge and completely written in Java. Through Paros’s proxy nature, all HTTP and HTTPS data between server and client, including cookies and form fields, can be intercepted and modified.
These proxies have a different purpose than those personal type proxies like Proxomitron which are intended to protect you, clean adverts, block spyware and so on. Proxies like Paros and Burp are meant for examining the security of applications and web application auditing.
You do need Java Run Time Enviroment (JRE) 1.4 (or above) to install Paros.
You can download the latest version of Paros Here.