TALES FROM THE CRYPTOGRAPHER
It would send chills down your spine to learn how easy it is for
others to connect to your Wi-Fi network and put your computers under
their spell. If your computer has been acting funny lately, working
fine at times while slowing to a crawl at others, it may have
crossed over to the dark side and could be spamming your friends and
scamming your parents.
A home network brings many benefits, but it can also expose new
evils. Both your Internet connection and your wireless router are
potential points of entry for the bad guys. Hackers can probe for
your computers over the Internet and turn them into zombies if they
are unprotected. Worms and viruses can slither their way through
your network, burrowing more holes into your PC than a
maggot-infested corpse, and the thief parked on the street where you
live can set up shop with the help of your Wi-Fi connection.
Here are a few tips that will keep hackers and freeloaders at bay.
1. Use encryption to protect your wireless network.
It sounds trivial, but consider this: wireless data is transmitted
over the air. This makes it far more exposed than data transmitted
over a cable. To hack into an Ethernet network, you either need to
force entry through an Ethernet connection or you need access to the
Ethernet cable, which you can lock behind a door; but to pry into a
wireless network, you need only be within range. A would-be intruder
can park in the street where you live and do her dirty work from the
privacy of her car, without risking the unpleasantries of breaking
and entering.
You can protect your wireless network by encrypting it. Virtually all Wi-Fi gear supports an encryption scheme called WEP (Wired Equivalent Privacy). WEP scrambles data transmitted over your network, making it difficult to decipher. Even better, setting up WEP is easy. In most cases, you merely enter a passphrase into the configuration settings of each device on your network. The devices use the passphrase to generate a WEP key, which is used to encrypt and decrypt data transmitted over the network.

2. Lock down your LAN. An always-on broadband
connection is convenient, but it's also a magnet for hackers and
script kiddies, giving them a target that is open 24/7. You can use
a firewall to thwart attacks on your network that use your Internet
connection as their point of entry. Most wireless routers come with
an integrated NAT firewall. NAT stands for network address
translation and is used to hide the IP addresses of the PCs on
your network behind your router's IP address. From the Internet,
your network appears to consist of only one device, your router.
This makes it more difficult for intruders to identify the computers
on your network. NAT, however, is relatively dumb. It maps the
addresses of the computers on your network to the IP address of the
router, but it doesn't inspect the data inside the packets passing
through your router. For that, you need a second firewall that
performs stateful packet inspection, or SPI. An SPI
firewall can determine if an incoming data packet is a legitimate
response to a request from one of your computers. Not all routers
include an SPI firewall, so keep a lookout for it when you buy your
gear.

3. Don't make it easy for criminals. Most consumer
networking gear is designed to be easy to use out of the box. Easy
setup might leave you with a warm fuzzy feeling after the initial
setup, but a foolproof setup routine can also leave your network
vulnerable to unwanted visitors. For example, routers use DHCP,
dynamic host configuration protocol, to automatically handle
the IP address information for the computers on your network. But
handing out IP address information automatically makes it easy for
unwanted guests to join your network. Consider manually assigning
static IP addresses to your computers and turning off your router's
DHCP server. To manually configure an IP address, right-click the
Network Neighborhood icon and select Properties. A window appears
listing your network adapters. Right-click the adapter you use to
connect to your LAN and select Properties. In the "Local area
connection properties" window that appears, select Internet Protocol
(TCP/IP) and click the button marked Properties. This window allows
you to use a pre-specified IP address, subnet mask, default gateway
(in this case, your router), and DNS server. Check
Wednesday's nightmare for more information about assigning IP
address information.
If you have a wireless router, it probably advertises its network
name, or SSID, at regular intervals to any device within range,
making it easy for others to join your wireless network. Some
routers let you turn off the beacon that puts your SSID on the air
for everyone to see. Since your computers presumably already know
your wireless network's SSID and have profiles instructing them to
use it for their connection, consider turning off your router's
beacon. Though not all routers let you turn the beacon off, many do.
Check the router's browser-based configuration tool for a beacon
switch.
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