... more Überhacker II, Chapter 18:
Ethernet Hacking: Wireless and Wired LANs
Following are examples from a wardriving session by William
Marchand of UnixHQ (http://www.unixhq.org)
using a Windows 2000 Professional laptop and Netstumbler.
Figure 1: Not connected yet.
He isnt connected to anything yet, as shown in Figure
1. However, he fires up Netstumbler and lo and behold, he sees
Figure 2: Bill is within range of a Wi-Fi access point
on Channel 6. Details are in the right hand panel.
Figure 3: It looks like a strong signal.
Figure 4: Time to get online!
Figure 5: The deed is done.
If you want to locate vulnerable WLANs in wholesale lots, there
is an even more interesting tool. At http://www.kismetwireless.net/ you can download
Kismet, a WLAN sniffer that also separates and identifies many
wireless networks in the area you are testing. A version of Kismet
for Linux, Kismet also supports FreeBSD, OpenBSD and MacOSX in
on the Überhacker CD-ROM.
Kismet works with any 802.11b wireless card that is capable of
reporting raw packets (rfmonsupport). These include any Prism2
based card (Linksys, D-Link, Rangelan, etc), Cisco Aironet cards,
and Orinoco based cards. Kismet also supports the WSP100 802.11b
remote sensor by Network Chemistry and is able to monitor 802.11a
networks with cards using the Ar5k chipset. Heres where
it gets interesting. There is a version that allows you to deploy
many Kismet sensors for distributed sniffing. Each "drone"
sensor sends packets over a TCP connection to a Kismet server.
Its output can be piped into Snort (http://www.snort.org)
and some other Intrusion Detection Systems (IDS).
You can get an idea of where easy-access Wi-Fi access points
exist in abundance at http://www.WiFiMaps.com/
maps. If you hunt on foot, keep an eye out for chalk marks
on sidewalks or walls. These often denote Wi-Fi access points.
If you would rather hunt while sitting in your hacker lab, you
can get into WLANs that are tens of kilometers away by using a
directional antenna. While a dog food can antenna as described
above is free, you can reach much further with an antenna designed
for the job. http://www.fab-corp.com/
is an example of a place where you can buy these.
There are many commercial products for detecting WLANs. They
are often used in companies that have problems with employees
setting up unauthorized access points. For example, AirMagnet
can run on the iPAQ PDA, and detects problems such as a Wi-Fi
access point advertising its SSID.
It is legal to detect WLANs, but not to use some of the wireless
systems you may access. It is best to make sure a WLAN is open
to the public before using it. However, unless it requires some
sort of authentication to log on, law enforcement wont
waste time pursuing casual visitors to WLANs. If you do this
and get busted anyhow, well, thats the risk you take in
any unauthorized computer access.
Now we come to the slightly hard part. How do you break in
if the WLAN asks for some sort of authentication? Wired Equivalent
Privacy (WEP) is a common way to authenticate, and can be broken
in minutes if you have a computer with a reasonably fast CPU.
Since some Wi-Fi hardware is incompatible with better ways than
WEP to authenticate, chances are you can find a lot of WEP nets
Airsnort is an example of a program that cracks WEP keys. Once
it has captured enough packets it can usually crack WEP in a second
or so, if running on Linux with a reasonably fast CPU. Airsnort
has varieties that run on BSD, Linux, OS X and Windows, and can
be downloaded at http://airsnort.shmoo.com/.
One version, for Unix-type operating systems, is on the Überhacker
Now we come to the super hard part: WiFi Protected Access
(WPA). Its the latest, greatest way to keep intruders from
abusing Wi-Fi. It can work, for example, with Windows Remote
Authentication Dial-In Services to authenticate users
and keep the uninvited out. At this writing no technique has
been publicized to break it. However, if by the time you read
this, a way has been discovered, here are some web sites that
are likely to offer downloads of the tools that do it, and instructions
for their use.