See data that an app is secretly sending to web server in the background

Question

I was playing around with fiddler (http proxy) and I noticed that some apps are making http get/post requests in the background and sending data and stats to and from the web. This got me interested and a little concerned to see what data various apps were sending but it seems that most of them are not doing it on port 80 via http but presumably on another port so you can't see the data in fiddler. Is there some way to view and/or potentially block the data being sent?

Answer 1

You're asking: "Using Fiddler, I saw that traffic was being sent by clients to servers. How can I see that traffic?"

Might I suggest you use Fiddler?

You can see the process sending the traffic in the Process column, and you can view the contents of the requests and responses using the Inspectors tab.

Answer 2

I would check out burp suite. It is a proxy you set up in your web browser and shows all of the data that passes through it. There's plenty of tutorials online. Check it out here