Rebroadcasting and monitoring wifi

Guides | Tutorial By 4 years ago

Free wifi is everywhere. It may seem like a godsend if you stumble upon a free wifi network, but watch out. A wifi network can be easily created just to steal your information.

I’m going to show just how easy it is to setup a fake free wifi network to monitor all network traffic going through it. To do this you will need two network cards, one will connect to an existing wifi network and the other will rebroadcast it out as “free wifi”. I will explore two different methods of doing this, but both have the same end result. I will use a Mac for both, but the same thing can be performed on Windows or Linux.

Method one: wireless usb adapter

A wireless usb adapter is made for connecting to wifi on the older computers that didn’t come with a wireless network card. If your computer already has a wireless network card you can use one for receiving and the other for transmitting. You can pick up one of these for as little as $15. I’ve got a Dlink DWA-110 I will use for this. I had to download some drivers to get it setup. First I connected to my own wifi using the usb adapter.


The next part is the same as using method two, so skip over to there for the next part.

Method two: a second computer

There’s probably more people with two computers compared to those that have a wifi usb adapter. You can connect one to wifi, then setup internet sharing through ethernet and then connect an ethernet cable from one computer to the other. This will let the 2nd computer use the internet from the first while keeping the wifi network card free for rebroadcasting.



Now you’re receiving internet you need to send it back out. On the Mac this is pretty easy, open the Sharing pane on System Preferences. Go to the internet sharing option the specify where you’re going to be sharing from. For me using method one with the DLink DWA-110 it’s from “802.11 bg WAN”, if you’re using method two it will always be from “Ethernet”. Select which one applies to you (Figure. 1 below). Now select how you want to share it, this will be the wifi option. When you select that, the wifi options button will become enabled. You can use this to change what wifi network name will be seen by others. I’ll call mine “Fast free wifi”. Finally turn it on on the left by ticking the internet sharing option.


The wifi icon in your status bar will turn into an up arrow. Now using another computer or a phone you should see your wifi network being broadcasted.

Any computer that connects has it’s internet traffic travelling through my computer. I can use a tool like Wireshark to spy on it, and see potentially sensitive information going through.