ead spectrum modulation technologies described in Chapter 4 were originally conceived for military applications where jamming was the main concern, any device conforming to a wireless standard such as 802.11b will be able to intercept wireless data traffic from a WLAN operating that standard. Additional security measures must be taken to prevent unauthorised access to user data and network resources. The easy accessibility of wireless networks resulted in a new industry springing up among the early adopters to map out networks and make others aware of the opportunity for free, although often illegal, access. War Driving and War Walking describe the pursuits of driving or walking around with a wireless enabled laptop or handheld device and seeking out wireless networks. War Chalking sprang up in London in 2002 as a way of making others aware of nearby wireless networks that could be freely accessed. Some WLANs are deliberately left without security measures enabled in order to allow Chapter Eight Open Node Closed Node Bandwidth Access contact WEP Node Bandwidth Figure 8-1: War Chalking; Table of Symbol Elements and Captions free public access, and War Chalking symbols were intended to help people living in or visiting a city to identify these networks in order to connect to the Internet (Figure 8-1). The site www.warchalking.org gives more information, as well as an interesting discussion on the legal and moral aspects of accessing unsecured WLANs. These free access points are of no interest to the determined hacker (or cracker), who is motivated by the challenge of breaking into a secured network. The measures described later in this chapter should be followed to ensure that access to a wireless network is as secure as it can be, and to minimise this risk of unauthorised access and use. At home, it is not just deliberate hackers who might see an unsecured wireless network as a free resource. If basic security measures are not enabled, any wireless enabled computer in a neighbouring house or apartment will be able