Scan for Wireless Networks #66
Chapter 8, Desktop Programs
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205
HACK
and create a thumbnail. Then it connects to the web server and changes to a
directory visible on the Internet. Once the script has completed, it deletes
any old screenshots and thumbnails and uploads the new ones. After it com-
pletes this job, it sleeps for 60 seconds by default (this is adjustable) and
then continues the loop once again.
Running the Code
To run the script first change the directory to $localfolder. Your
autoscreenshot.pl script should be sitting in this folder. Now you can run it
in two different ways. You can run the script independently with the follow-
ing commands:
foo@bar:~$ chmod 777 autoscreenshot.pl
foo@bar:~$ ./autoscreenshot.pl
An alternative is to run it with the Perl interpreter:
foo@bar:~$ perl autoscreenshot.pl
—John Cheng
HACK
#66
Scan for Wireless Networks Hack #66
Detect which networks are available in your area.
Wireless networks are rapidly gaining use in homes, businesses, schools,
and other places. You can often access these networks for your personal use.
As an example, if you are visiting a conference and a number of different
wireless networks are available, you need to be able to distinguish one net-
work from another and log on. To discover which networks are available to
you, you need to use a network scanner.
Another reason to scan a network is to determine how wide-reaching and
secure the network is. If you are running a wireless network that is not
encrypted, a house down the street might be able to connect and gain free
access to your LAN. In some cases, you might want to have an open net-
work (some people leave their wireless networks open to create free Internet
hotspots), but in other cases, this might be expressly what you don’t want.
Although anyone can connect to a wireless network easily enough, scanning
for networks is a different ballgame. First of all, you need to put your net-
work card into a special mode called monitor mode that can scan for net-
works, and then you need to be able to control the card to determine when a
network has been detected. You can achieve all of this with a suitable wire-
less card and a tool called Kismet (http://www.kismetwireless.net).

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