Making Sense of Evolving WLAN Standards, Part 1: Security - Page 2

By Jeff Vance

January 05, 2004

Standards Can't Plug Every Security Hole

It's important to distinguish here between what vendors should be responsible for and where customer accountability comes in. Remember, many of the crackable WLANs out there are easily cracked because encryption and authentication of any flavor are turned off. You can't blame the bank-vault manufacturer if the bank manager never locks the vault because he doesn't want to bother memorizing the combination.

Even so, because of the hysteria surrounding wireless security, vendors are addressing the lazy-bank-manager problem by centralizing security into the core of the network, moving it away from access points and into a single, centralized appliance, such as a WLAN switch.

However, then you have yet another problem: your APs may have enough information in them to put your network at risk.

"Access points are inherently vulnerable because they are not physically secure. A savvy hacker or a smart disgruntled employ could guess the AP password and modify security settings to allow open network access," DeBeasi said. "A switch raises the bar because it requires more sophisticated control protocols such as SNMP version 3."

Bluesocket's Juitt says, "Both WPA and 802.11i should provide reasonable Layer 2 security, but any security professional with an ounce of sense will tell you that secure networks, be they wired or wireless, are based on a layered security architecture. You begin with the underlying Layer 2 protocols and build up from there. In some deployments, a Layer 2 solution is enough. In others, you may want to add Layer 3 security, perhaps IPSec, on top of that."

A common method for strengthening WLANs beyond Layer 2 encryption is to utilize an existing wired standard such as IPSec and run virtual private network (VPN) tunnles over your WLAN. However, VPNs are notorious for being complex and management intensive. Moreover, since VPNs provide Layer 3 security, they are still vulnerable to Layer 2 attacks. With a Layer 3 security solution, any node trying to access the network must do so by being granted Layer 2 access to begin with. With the data link unprotected, an attacker can see MAC addresses , associate with Access Points, and receive an IP address from the Dynamic Host Configuration Protocol (DHCP) server. Of course, much of the problem here stems from the fact that IPSec is intended as a point-to-point protocol, while WLANs are broadcast networks.

In contrast to IPSec, both WPA and 802.11i encrypt traffic and enforce user authentication at layer 2 using IEEE 802.1x. IEEE 802.1x uses EAP (Extensible Authentication Protocol) to provide the ability to conduct centralized authentication and dynamic key exchange. EAP packets are carried at the MAC layer over the WLAN and are then forwarded to the RADIUS server by the WLAN switch/AP. 802.1x also enables centralized policy control, so session time-outs can be enforced and automatic key redistribution can be mandated.

Security Is a Moving Target

This whole issue of strong-enough WLAN security standards reminds me of several conversations I've had with security guru Bruce Schneier, founder and CTO of Counterpane Internet Security and author of several books on security, including Secrets & Lies: Digital Security in a Networked World. You can't have a conversation with Schneier without hearing two security refrains repeated over and over: "Security is a process, not a product," and "Security is a moving target." In other words, there is human intelligence involved with any type of network attack, so those attacks constantly evolve. Products can address known vulnerabilities, but they tend to be blindsided by innovative attack methods.

While it would be foolish to believe that wireless security issues will ever be solved, I have noticed lately that my discussions about WLAN security are strikingly similar to the conversations I was having a couple of years ago about wired Internet security. In other words, the security gap between the two is rapidly closing (you could argue it has closed already). Instead of worrying about security holes you can drive a truck through (like WEP), the industry is beginning to worry about more savvy, creative, and sophisticated security issues. If you have an 802.11i- or WPA-compliant WLAN that centralizes authentication and policy procedures, then wireless security is no longer an issue of wireless security, but simply of network security.

(Part Two of this article will investigate the issues that arise once security concerns have been taken off the table. Which version of radio technology should you commit to -- 802.11a, b, or g? And once the client-to-radio communication is addressed, how then should your radios communicate back to your centralized WLAN appliance?)

Jeff Vance is a technology writer and consultant. He was previously the editor of Mobile Internet Times and E-Infrastructure Times, before striking out as a freelance writer. He now focuses on high-tech trends in wireless, next-generation networking, and Internet infrastructure. His articles have appeared or are forthcoming in Network World, Wi-Fi Planet,,, and Telecom Trends, among others. You can contact him at

Pages: 1 2

Comment and Contribute
(Maximum characters: 1200). You have
characters left.