ZDNet UK / News and Analysis / Business of IT / IT Strategy

BT: It's not good to chalk

By Graeme Wearden, ZDNet.co.uk, 27 September, 2002 16:55

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Wireless, warchalking, BTOpenworld, Security, Wi-Fi

NEWS
BTopenworld is warning of the dangers of operating insecure wireless local area networks, claiming that warchalking can encourage malicious hackers to break into corporate networks. In a guide released this week, the ISP says that the rise of warchalking -- where enthusiasts mark the presence of Wi-Fi networks so that other users can enjoy free wireless Internet access -- shows that companies must pay more attention to the security of their wireless networks. "Whilst the general idea of sharing your bandwidth with the outside world may seem like a clever idea to some, there are of course security risks associated with it," cautioned BTopenworld. "Whilst many people externally accessing your network may simply be doing it to use your bandwidth rent free for a short period of time the effect may also slow down your network and create significant security issues if your network is not secure," the ISP added. Warchalkers insisted that their activities are not harmful, and have strongly rejected the claim that gaining unauthorised access to a WLAN is theft. According to warchalking.org -- which also points out that some warchalking symbols are actually drawn by the person who owns or operates the wireless network -- the activity is not dangerous. "Using someone's wireless network doesn't take anything -- they still have everything they had previously. Nor does it prevent them from using their network; in most cases (they're not likely to) notice," wrote one warchalker last week. BTopenworld, though, insists that an unprotected network is vulnerable to attack from malicious hackers. "Companies need to ensure that no unauthorised person can 'eavesdrop' onto data traffic and gain unauthorised access onto corporate networks," said BTopenworld. The warchalking phenomenon sprung up in response to the proliferation of insecure corporate Wi-Fi networks, as many companies installed WLANs but failed to set up the necessary security. Because of this, BTopenworld has laid out the security measure that companies should take. The measures are reproduced below, but BTopenworld warns that its guide is for information purposes only, and should not be used as a substitute for specialist advice on a company's network security. Simple solutions
At the initial set-up phase of your WLAN, you should implement at least this basic security:
  • Change the default SSID (Service Set ID or network name) and encryption keys.
  • Filter MAC addresses at the access point to allow access to known users only.
  • Enable WEP (Wired Equivalent Privacy - see below) at the highest level possible and change regularly.
  • Limit folder/file sharing to the minimum with password protection.
  • Install firewalls on all connected PC's.
  • Install an updatable virus checker.
Around 40 percent of WLAN users do not modify original manufacturer default passwords and do not enable WEP. This is equivalent to leaving the front door wide open. Service Set ID and Wired Equivalent Privacy are the two primary built-in security features within the 802.11b WLAN standard. SSID is the method by which different roaming networks identify themselves. It is also used as a basic password without which the user cannot log onto the network. However, the access point can be configured to broadcast the SSID number -- and this is often the case where users configure the equipment themselves. Broadcast should be turned off and default passwords changed. The 802.11b standard WLAN also includes 40 and 64-bit encryption that decreases the likelihood of eavesdropping. WEP encryption allows the user 4 basic options from no encryption to an authentication and encryption solution, which prevents unauthorised access as well as encoding the data carried over the network. Some equipment, such as that provided by Linksys / BTopenworld, allows 128-bit WEP encryption, which can be user defined. This offers a stronger, and therefore safer, cipher of the data on the WLAN. This is not an unbreakable barrier to professional hackers but does offer significant protection against script kiddies and drive by hacking. Furthermore, 128-bit WEP will probably delay any attack to such an extent that there is usually time for the intrusion to be detected. If you think your business may be targeted by 'professional' hackers with expensive equipment and unlimited time to spend in trying to access your network, then you may need to take additional security measures. Additional Security Measures
Businesses who wish to protect themselves from professional hackers should implement additional security measures such as those listed below:
  • Ensure all access points are outside the firewall (i.e. treat the WLAN as external to the corporate LAN).
  • Use IPsec or SSH encryption
  • Consider RADIUS authentication procedures
  • Use separate secure logon methods for access to the corporate LAN
  • Locate access points in the centre of the building -- minimising radiation of the signal outside the building
  • Remove "rogue" -- unauthorised -- access points from the network.
  • Password protect all files and folders.
Finally, for an even safer security set-up WLAN users should consider creating a IPsec VPN. In this configuration each device (client and network) is fully authenticated and communicates via an encrypted VPN 'tunnel'. This does require additional network hardware to terminate the connection tunnels and form bridging functions to other networks, such as wired ethernet. It also requires a VPN client application on each wireless device using the network. This can be an expensive option that is normally only used by large businesses.
For all security-related news, including updates on the latest viruses, hacking exploits and patches, check out ZDNet UK's Security News Section. Have your say instantly, and see what others have said. Go to the Security forum. Let the editors know what you think in the Mailroom.

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