Wired computer networks are costly to install and difficult to change, wireless networks on the other hand are now cheap to install and very flexible. Wireless makes it possible connect equipment in large warehouses, retail sites and manufacturing plants without the need to install cabling. It is possible to move equipment without the need for technical assistance and, in the most extreme case, a complete installation can be moved from one building to another. However this flexibility comes with a price.
Because of the nature of wireless it is possible that private signals can be picked up by people outside and that outsiders could connect into private Wireless Local Area Networks (WLANs). This has led to the emergence of 'warchalking' and 'wardriving' threats. Wardriving involves using a laptop computer with a WLAN card and wireless scanner software in a car to detect wireless networks. When they have discovered a wireless network with external connectivity some individuals will share the details using symbols chalked on pavements or walls ('warchalking'). This has recently been the subject of some media hype so what is the real nature of this threat?
Wireless Local Area Networks provide wireless access over a range of up to several hundred feet. The prevailing specification used to implement WLANs today is the IEEE's 802.11b and WLANs are sometimes referred to as 802.11x networks. In order to provide privacy this standard defines Wired Equivalence Privacy (WEP) encapsulation of data. However, despite having well known encryption mechanisms, namely the RC4 cipher, WEP is vulnerable to both passive and active attacks. This opens up the wireless network to malicious parties to eavesdrop and tamper with wireless transmissions.
So how far does a WLAN reach? 802.11b facilitates the wireless transmission of up to a maximum of 11 Mbps (Mega bits per second) of data at distances ranging from a few feet to several hundred feet over the standard 2.4 GHz (Giga Hertz) unlicensed band. However radio amateurs in the UK noticed that the lowest six channels of the WLAN band fall into the 2.3 - 2.45 GHz amateur radio band. So, liking a challenge, they set out to see how far they could make a WLAN reach (working DX in ham parlance). According to the article published on the Flight Refueling Amateur Radio web site (http://www.frars.org.uk) they were able to use the WLAN across 14km. This emphasizes how important it is to adjust the transmission level of your base station to be just sufficient for your needs.
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