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Page 41 / 61 Scroll up to view Page 36 - 40
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Appendix B: Wireless Security
A Brief Overview
Wireless-G Access Point
Appendix B: Wireless Security
A Brief Overview
Whenever data - in the form of files, emails, or messages - is transmitted over your wireless network, it is open
to attacks. Wireless networking is inherently risky because it broadcasts information on radio waves. Just like
signals from your cellular or cordless phone can be intercepted, signals from your wireless network can also be
compromised. What are the risks inherent in wireless networking? Read on.
What Are The Risks?
Computer network hacking is nothing new. With the advent of wireless networking, hackers use methods both
old and new to do everything from stealing your bandwidth to stealing your data. There are many ways this is
done, some simple, some complex. As a wireless user, you should be aware of the many ways they do this.
Every time a wireless transmission is broadcast, signals are sent out from your wireless PC or access point, but
not always directly to its destination. The receiving PC or access point can hear the signal because it is within
that radius. Just as with a cordless phone, cellular phone, or any kind of radio device, anyone else within that
radius, who has their device set to the same channel or bandwidth can also receive those transmission.
Wireless networks are easy to find. Hackers know that, in order to join a wireless network, your wireless PC will
typically first listen for "beacon messages". These are identifying packets transmitted from the wireless network
to announce its presence to wireless nodes looking to connect. These beacon frames are unencrypted and
contain much of the network's information, such as the network's SSID (Service Set Identifier) and the IP address
of the network PC or access point. The SSID is analogous to the network's name. With this information broadcast
to anyone within range, hackers are often provided with just the information they need to access that network.
One result of this, seen in many large cities and business districts, is called "Warchalking". This is the term used
for hackers looking to access free bandwidth and free Internet access through your wireless network. The marks
they chalk into the city streets are well documented in the Internet and communicate exactly where available
wireless bandwidth is located for the taking.
Even keeping your network settings, such as the SSID and the channel, secret won't prevent a hacker from
listening for those beacon messages and stealing that information. This is why most experts in wireless
networking strongly recommend the use of WEP (Wired Equivalent Privacy). WEP encryption scrambles your
wireless signals so they can only be recognized within your wireless network.
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Appendix B: Wireless Security
What Are The Risks?
Wireless-G Access Point
But even WEP has its problems. WEP's encryption algorithm is referred to as "simple", which also means
"weak", because the technology that scrambles the wireless signal isn't too hard to crack for a persistent
hacker.
There are five common ways that hackers can break into your network and steal your bandwidth as well as your
data. The five attacks are popularly known as:
1.
Passive Attacks
2.
Jamming Attacks
3.
Active Attacks
4.
Dictionary-building or Table Attacks
5.
Man-in-the-Middle Attacks
Passive Attacks
There's no way to detect a passive attack because the hacker is not breaking into your network. He is simply
listening (eavesdropping, if you will) to the information your network broadcasts. There are applications easily
available on the Internet that can allow a person to listen into your wireless network and the information it
broadcasts. Information such as MAC addresses, IP addresses, usernames, passwords, instant message
conversations, emails, account information, and any data transmitted wirelessly, can easily be seen by someone
outside of your network because it is often broadcast in clear text. Simply put, any information transmitted on a
wireless network leaves both the network and individual users vulnerable to attack. All a hacker needs is a
"packet sniffer", software available on the Internet, along with other freeware or shareware hacking utilities
available on the Internet, to acquire your WEP keys and other network information to defeat security.
Jamming Attacks
Jamming Attacks, when a powerful signal is sent directly into your wireless network, can effectively shut down
your wireless network. This type of attack is not always intentional and can often come about simply due to the
technology. This is especially possible in the 2.4 GHz frequency, where phones, baby monitors, and microwave
ovens can create a great deal of interference and jam transmissions on your wireless network. One way to
resolve this is by moving your wireless devices into the 5 GHz frequency, which is dedicated solely to information
transmissions.
Important:
Always remember that each
device in your wireless network MUST use
the same encryption method and encryption
key or your wireless network will not function
properly.
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Appendix B: Wireless Security
Maximizing Wireless Security
Wireless-G Access Point
Active Attacks
Hackers use Active Attacks for three purposes: 1) stealing data, 2) using your network, and 3) modifying your
network so it's easier to hack in the next time.
In an Active Attack, the hacker has gained access to all of your network settings (SSID, WEP keys, etc.) and is in
your network. Once in your wireless network, the hacker has access to all open resources and transmitted data
on the network. In addition, if the wireless network's access point is connected to a switch, the hacker will also
have access to data in the wired network.
Further, spammers can use your Internet connection and your ISP's mail server to send tens of thousands of e-
mails from your network without your knowledge.
Lastly, the hacker could make hacking into your network even easier by changing or removing safeguards such
as MAC address filters and WEP encryption. He can even steal passwords and user names for the next time he
wants to hack in.
Dictionary-Building or Table Attacks
Dictionary-building, or Table attacks, is a method of gaining network settings (SSID, WEP keys, etc.) by analyzing
about a day's worth of network traffic, mostly in the case of business networks. Over time, the hacker can build
up a table of network data and be able to decrypt all of your wireless transmissions. This type of attack is more
effective with networks that transmit more data, such as businesses.
Man-in-the-Middle Attacks
A hacker doesn't need to log into your network as a user - he can appear as one of the network's own access
points, setting himself up as the man-in-the-middle. To do this, the hacker simply needs to rig an access point
with your network's settings and send out a stronger signal that your access point. In this way, some of your
network's PCs may associate with this rogue access point, not knowing the difference, and may begin sending
data through it and to this hacker.
The trade-off for the convenience and flexibility wireless networking provides is the possibility of being hacked
into through one of the methods described here. With wireless networks, even with WEP encryption, open to the
persistent hacker, how can you protect your data? The following section will tell you how to do just that.
Maximizing Wireless Security
Security experts will all tell you the same thing: Nothing is guaranteed. No technology is secure by itself. An
unfortunate axiom is that building the better mousetrap can often create a better mouse. This is why, in the
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Appendix B: Wireless Security
Maximizing Wireless Security
Wireless-G Access Point
examples below, your implementation and administration of network security measures is the key to maximizing
wireless security.
No preventative measure will guarantee network security but it will make it more difficult for someone to hack
into your network. Often, hackers are looking for an easy target. Making your network less attractive to hackers,
by making it harder for them to get in, will make them look elsewhere.
How do you do this? Before discussing WEP and WPA, let's look at a few security measures often overlooked.
A.
Common Sense Solutions
1)Network Content
Now that you know the risks assumed when networking wirelessly, you should view wireless networks as you
would the Internet. Don't host any systems or provide access to data on a wireless network that you wouldn't put
on the Internet.
2)Network Layout
When you first lay out your network, keep in mind where your wireless PCs are going to be located and try to
position your access point(s) towards the center of that network radius. Remember that access points transmit
indiscriminately in a radius; placing an access point at the edge of the physical network area reduces network
performance and leaves an opening for any hacker smart enough to discover where the access point is
transmitting.
This is an invitation for a man-in-the-middle attack, as described in the previous section. To perform this type of
attack, the hacker has to be physically close to your network. So, monitoring both your network and your property
is important. Furthermore, if you are suspicious of unauthorized network traffic, most wireless products come
with a log function, with which you can view activity on your network and verify if any unauthorized users have
had access.
3)Network Devices
With every wireless networking device you use, keep in mind that network settings (SSID, WEP keys, etc.) are
stored in its firmware. If they get into the hands of a hacker, so do all of your settings. So keep an eye on them.
4)Administrator passwords
Your network administrator is the only person who can change network settings. If a hacker gets a hold of the
administrator's password, he, too, can change those settings. So, make it harder for a hacker to get that
information. Change the administrator's password regularly.
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41
Appendix B: Wireless Security
Maximizing Wireless Security
Wireless-G Access Point
5)SSID
There are a few things you can do to make your SSID more secure:
a. Disable Broadcast
b. Make it unique
c. Change it often
Most wireless networking devices will give you the option of broadcasting the SSID. This is a option for
convenience, allowing anyone to log into your wireless network. In this case, however, anyone includes hackers.
So don't broadcast the SSID.
A default SSID is set on your wireless devices by the factory. (The Linksys default SSID is "linksys".) Hackers
know these defaults and can check these against your network. Change your SSID to something unique and not
something related to your company or the networking products you use.
Changing your SSID regularly will force any hacker attempting to gain access to your wireless network to start
looking for that new SSID.
With these three steps in mind, please remember that while SSIDs are good for segmenting networks, they fall
short with regards to security. Hackers can usually find them quite easily.
6)MAC addresses
Enable MAC address filtering if your wireless products allow it. MAC address filtering will allow you to provide
access to only those wireless nodes with certain MAC addresses. This makes it harder for a hacker using a
random MAC address or spoofing (faking) a MAC address.
7)Firewalls
Once a hacker has broken into your wireless network, if it is connected to your wired network, they'll have
access to that, too. This means that the hacker has effectively used your wireless network as a backdoor through
your firewall, which you've put in place to protect your network from just this kind of attack via the Internet.
You can use the same firewall technology to protect your wired network from hackers coming in through your
wireless network as you did for the Internet. Rather than connecting your access point to an unprotected switch,
swap those out for a router with a built-in firewall. The router will show the access point coming in through its
WAN port and its firewall will protect your network from any transmissions entering via your wireless network.

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