Security
When wireless networking was new and rare, security was somewhat of an afterthought, because the scarcity of 802.11b cards acted as a form of back-handed security.
If no one had a wireless card, outsiders couldn't very well scan your setup. Now, however, that's changed. Wireless equipment is cheap and readily available so that almost anyone with a PC can afford a wireless network card, making security more vital.
Wireless networks are less secure than wired networks, because they transfer data through the air and are more vulnerable to eavesdropping and unauthorised use. Any laptop with some network sniffing software could be used to monitor network and steal data or bandwidth without the need for a physical network connection.
There are two main problems associated with unauthorised network access. The most common problem is that a would-be cracker is generally inside your firewall, and therefore behind your first, and probably strongest line of defense.
The second problem is that of "bandwidth jacking" where someone could set up a permanent machine (on the roof, in the building next door etc), which makes unauthorised use of your bandwidth, causing either legal problems, or excessive download costs, or both.
Standards, standards, standards
In an attempt to stop attacks from would-be crackers, the 802.11b standards implement what is called the wired equivalency protocol (WEP). The idea is that this protocol will protect network privacy. As a secondary function, WEP is used to prevent unauthorised access to the wireless network.
Unfortunately, many wireless networks are just set up as a quick "test" of the technology, and are often then left in use without even the most basic security features turned on.
There has been much research into the effectiveness of the protocol, and it has found that it is subject to several attacks, including passive attacks to decrypt traffic based on statistical analysis, active attacks to inject new traffic from unauthorised mobile stations, based on known plaintext passwords, and active attacks to decrypt traffic, based on tricking the access point.
The WEP protocol relies on a secret key that is shared by the access point and a set of nodes. This key is used to encrypt data packets before they are transmitted.
The packets are also checked for integrity to ensure that they have not been modified in transit. One flaw of the 802.11 standard is that it does not address the issue of how shared keys are to be established. In most implementations of wireless networks this is a single key that is shared between each node and access point and is manually set.
The problems with this encryption method lie in the heart of the encryption algorithm. WEP uses the RC4 algorithms, which lend themselves to several types of attacks.
One such attack is the changing of a bit by an attacker in an intercepted packet. In doing so, the data that will be decrypted will be corrupted.
Another can lead to the ability to recover all plaintexts sent. In this attack, the eavesdropper need only to intercept two packets encrypted with the same key stream. With this, it is possible to use statistical attacks to obtain the plaintext key.
In recent times, there have been a variety of methods proposed to upgrade the security of wireless networks, including the passing of 128bit encrypted short use keys in both directions. Another option is to have access to the Wireless network controlled by a VPN.
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The January 2002 issue of ZDNet Australia's Technology & Business Magazine contains reviews of wireless LAN products, including Editor's Choice Awards for the best products. For subscription information, visit Technology & Business.
