Are people abusing your wireless network? Do you want to keep your kids offline at night? Do you want to break the network of your school, office, or local coffeeshop?
Then WiFiKill is your weapon.
WiFiKill turns your phone into a rogue access point that drops the packets of every computer, phone, tablet or other device that you choose to block. You can keep your boss offline, throw your teachers out of the school network, cut your husbands access to online porn, or simply disable internet connections for each and every device made by Apple, Inc.
You don't even need to own the network (although WiFiKill lets you p3wn it), because it works on all wireless networks that you can connect to, whether they're encrypted or not.
You get a choice of methods to play the bad guy. The default method will simply drop all packets for the devices that you select. If you enable IP tables you can reject packets or redirect all requests to a bogus IP address (like the loopback address 127.0.0.1). You can't redirect traffic to an address of your choice, which is a good thing since this would allow you to send everyone on the network to a virus server.
Update: WiFiKill got even more deadly. Now you can redirect your victims to your fake PayPal login screen.
There is a price to pay, however. Since your victims believe your phone is the router, your WiFi will get flooded. If you block everyone on a large network you'll get so much incoming traffic on your phone that your own internet connection will suffer and your battery will drain like crazy.
WiFiKill doesn't spoof your MAC address, so you may get caught. And even if you get away, your phone will probably be banned forever by the network administrator. Worse yet, the network owner can just wait until you return to the network later and send out some sort of identifiable information like an email address or Facebook login. Of course WiFiKill can also get you expelled, fired, dumped, divorced, locked up, or murdered, so don't go killing networks at random.
By default WiFiKill loads a long list of hardware vendors so you can see who made the devices connected to the network. This list loads real slow, but you can speed up the app by disabling the vendor list. If you do so, you'll only see MAC addresses, not device types.
WiFiKill needs a rooted phone to work and
Update: WiFiKill got booted off the Android Market, but you can download the free version straight from its maker.
• Things change. Go read all about the new WiFiKill.
• Protect yourself against WiFiKill with Wifi Protector