EvilZone

You can easily do it on an android phone with the help of Zanti (a mobile pentesting app). You scan the whole network and then it shows you all the connected devices, tap on the one you want and then a new screen comes up with more options like running a script, connecting to a remote port on the target, shell shock, SSL poodle and for the one that your looking for MITM you get Lots of ways to play with anyone you would like to hit with just a click of a few buttons. Go to MITM and turn on SSL strip if the target is visiting a secured site but since you want to go for the router i doubt you'll be needing that. Now that you're done with that the next thing you want to do is turn MITM on it should be on the top right side on your screen then go to logged requests here is where you get live traffic of your target whenever the target visits a site and logs in the login credentials are displayed you can either jack that logged in session or just copy the username and password and login to the router manually.

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