Wireless Security

By default, wireless security is nonexistent on access points and clients. The original 802.11 committee just didn’t imagine that wireless hosts would one day outnumber bounded media hosts, but that’s truly where we’re headed. Also, and unfortunately, just like with the IPv4 routed protocol, engineers and scientists didn’t add security standards that are robust enough to work in a corporate environment. So we’re left with proprietary solution add-ons to aid us in our quest to create a secure wireless network.

Open Access

All Wi-Fi Certified wireless LAN products are shipped in “open-access” mode, with their security features turned off. While open access or no security may be appropriate and acceptable for public hot spots such as coffee shops, college campuses, and maybe airports, it’s definitely not an option for an enterprise organization, and likely not even adequate for your private home network. Security needs to be enabled on wireless devices during their installation in enterprise environments. It may come as quite a shock, but some companies actually don’t enable any WLAN security features. Obviously, the companies that do this are exposing their networks to tremendous risk! The reason that the products are shipped with open access is so that any person who knows absolutely nothing about computers can just buy an access point, plug it into their cable or DSL modem, and they’re up and running.

SSIDs, WEP, and MAC Address Authentication

What the original designers of 802.11 did to create basic security was include the use of Service Set Identifiers (SSIDs), open or shared-key authentication, static Wired Equivalency Protocol (WEP), and optional Media Access Control (MAC) authentication. Sounds like a lot, but none of these really offer any type of serious security solution-all they may be close to adequate for is use on a common home network.

SSID is a common network name for the devices in a WLAN system that create the wireless LAN. An SSID prevents access by any client device that doesn’t have the SSID. The thing is, by default, an access point broadcasts its SSID in its beacon many times a second. And even if SSID broadcasting is turned off, a bad guy can discover the SSID by monitoring the network and just waiting for a client response to the access point. Why? Because, that information, as regulated in the original 802.11 specifications, must be sent in the clear.

Two types of authentication were specified by the IEEE 802.11 committee: open and shared-key authentication. Open authentication involves little more than supplying the correct SSID-but it’s the most common method in use today. With shared-key authentication, the access point sends the client device a challenge-text packet that the client must then encrypt with the correct Wired Equivalency Protocol (WEP) key and return to the access point. Without the correct key, authentication will fail and the client won’t be allowed to associate with the access point. But shared-key authentication is still not considered secure because all an intruder has to do to get around this is detect both the clear-text challenge and the same challenge encrypted with a WEP key and then decipher the WEP key.

With open authentication, even if a client can complete authentication and associate with an access point, the use of WEP prevents the client from sending and receiving data from the access point unless the client has the correct WEP key. A WEP key is composed of either 40 or 128 bits and, in its basic form, is usually statically defined by the network administrator on the access point and all clients that communicate with that access point. When static WEP keys are used, a network administrator must perform the time-consuming task of entering the same keys on every device in the WLAN.

Last, client MAC addresses can be statically typed into each access point, and any of them that show up without that MAC addresses in the filter table would be denied access. Sounds good, but of course all MAC layer information must be sent in the clear-anyone equipped with a free wireless sniffer can just read the client packets sent to the access point and spoof their MAC address.

WPA or WPA 2 Pre-Shared Key

Although this is another form of basic security that’s really just an add-on to the specifications, WPA or WPA2 Pre-Shared Key (PSK) is a better form of wireless security than any other basic wireless security method mentioned so far. The PSK verifies users via a password or identifying code (also called a passphrase) on both the client machine and the access point. A client only gains access to the network if its password matches the access point’s password. The PSK also provides keying material that TKIP or AES uses to generate an encryption key for each packet of transmitted data. While more secure than static WEP, PSK still has a lot in common with static WEP in that the PSK is stored on the client station and can be compromised if the client station is lost or stolen even though finding this key isn’t all that easy to do. It’s a definite recommendation to use a strong PSK passphrase that includes a mixture of letters, numbers, and nonalphanumeric characters. Wi-Fi Protected Access (WPA) is a standard developed in 2003 by the Wi-Fi Alliance, formerly known as WECA. WPA provides a standard for authentication and encryption of WLANs that’s intended to solve known security problems existing up to and including the year 2003. This takes into account the well-publicized AirSnort and man-in-the-middle WLAN attacks.

WPA is a step toward the IEEE 802.11i standard and uses many of the same components, with the exception of encryption-802.11i uses AES encryption. WPA’s mechanisms are designed to be implementable by current hardware vendors, meaning that users should be able to implement WPA on their systems with only a firmware/software modification.

Cisco Unified Wireless Network Security

The Cisco Unified Wireless Network delivers many innovative Cisco enhancements and supports Wi-Fi Protected Access (WPA) and Wi-Fi Protected Access 2 (WPA2), which provide access control per user, per session via mutual authentication and data privacy and through strong dynamic encryption. Quality of service (QoS) and mobility are integrated into this solution to enable a rich set of enterprise applications. The Cisco Unified Wireless Network provides the following:

Secure Connectivity for WLANs – Strong dynamic encryption keys that automatically change on a configurable basis to protect the privacy of transmitted data.

  • WPA-TKIP includes encryption enhancements like MIC, per-packet keys via initialization vector hashing, and broadcast key rotation.
  • WPA2-AES is the “gold standard” for data encryption.

Trust and Identity for WLANs A robust WLAN access control that helps to ensure that legitimate clients associate only with trusted access points rather than rogue, or unauthorized access points. It’s provided per user, per session via mutual authentication using IEEE 802.1X, a variety of Extensible Authentication Protocol (EAP) types, a Remote Authentication Dial-In User Service (RADIUS), and a Authentication, Authorization, and Accounting (AAA) server. It supports the following:

    • The broadest range of 802.1X authentication types, client devices, and client operating systems on the market.

RADIUS accounting records for all authentication attempts.

Threat Defense for WLANs – Detection of unauthorized access, network attacks, and rogue access points via an Intrusion Prevention System (IPS), WLAN NAC, and advanced location services. Cisco’s IPS allows IT managers to continually scan the RF environment, detect rogue access points and unauthorized events, simultaneously track thousands of devices, and mitigate network attacks. NAC has been specifically designed to help ensure that all wired and wireless endpoint devices like PCs, laptops, servers, and PDAs that are trying to access network resources are adequately protected from security threats. NAC allows organizations to analyze and control all devices coming into the network.

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