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Securing Wireless Networks

Many different strategies and protocols are used to secure LAN and WAN transmissions. What about network transmissions that travel over the airwaves?

In the last few years, wireless networking has changed the look of modern networks, bringing with it an unparalleled level of mobility and a host of new security concerns.

Wireless LANs (WLANs) require new protocols and standards to handle security for radio communications. As it stands today, wireless communications represent a significant security concern. You should be aware of a few wireless security standards when working with wireless, including Wired Equivalent Privacy (WEP), Wi-Fi Protected Access (WPA), and 802.1X.

Wired Equivalent Privacy (WEP)

Wired equivalent privacy (WEP) was the first attempt to keep wireless networks safe. WEP was designed to be easy to configure and implement. Originally it was hoped that WEP would provide the same level of security to wireless networks as was available to wired. For a time it was the best and only option for securing wireless networks.

WEP is an IEEE standard introduced in 1997, designed to secure 802.11 networks. With WEP enabled, each data packet transmitted over the wireless connection would be encrypted. Originally, the data packet was combined with a secret 40-bit number key as it passed through an encryption algorithm known as RC4. The packet was scrambled and sent across the airwaves. On the receiving end, the data packet passed through the RC4 backward, and the host received the data as it was intended. WEP originally used a 40-bit number key, but later it specified 128-bit encryption, making WEP that much more robust.

WEP is a protocol designed to provide security by encrypting data from the sending and receiving devices. In a short period of time, however, it was discovered that WEP encryption was not nearly as secure as hoped. Part of the problem was that when the 802.11 standards were being written, security was not the major concern it is today. As a result, WEP security was easy to crack with freely available hacking tools. From this point, wireless communication was regarded as a potentially insecure transmission medium.

The two types of WEP security are static and dynamic. Dynamic and static WEP differ in that dynamic WEP changes security keys periodically, making it more secure. Static WEP uses the same security key on an ongoing basis. The primary security risks are associated with static WEP, which uses a shared password to protect communications. Security weaknesses discovered in static WEP mean that WLANs protected by it are vulnerable to several types of threats. Freely available hacking tools make breaking into static WEP-protected wireless networks a trivial task. Unsecured WLANs are obviously exposed to these same threats as well; the difference is that less expertise, time, and resources are required to carry out the attacks.

Wi-Fi Protected Access (WPA)

Security weaknesses associated with WEP gave administrators a valid reason to be concerned about wireless security. The need for increased wireless security was important for wireless networking to reach its potential and to reassure those who had sensitive data that it was safe to use wireless communications. In response, Wi-Fi Protected Access (WPA) was created. WPA was designed to improve on the security weaknesses of WEP and to be backward-compatible with older devices that used the WEP standard. WPA addressed two main security concerns:

  • Enhanced data encryption: WPA uses a temporal key integrity protocol (TKIP), which scrambles encryption keys using a hashing algorithm. Then the keys are issued an integrity check to verify that they have not been modified or tampered with during transit.
  • Authentication: Using Extensible Authentication Protocol (EAP), WEP regulates access to a wireless network based on a computer’s hardware-specific MAC address, which is relatively simple to be sniffed and stolen. EAP is built on a more secure public-key encryption system to ensure that only authorized network users can access the network.

802.1X

802.1X is an IEEE standard specifying port-based network access control. 802.1X was not specifically designed for wireless networks; rather, it provides authenticated access for both wired and wireless networks. Port-based network access control uses the physical characteristics of a switched local area network (LAN) infrastructure to authenticate devices attached to a LAN port and to prevent access to that port in cases where the authentication process fails. The 802.1X framework has three main components:

  • Supplicant: The system or node requesting access and authentication to a network resource.
  • Authenticator: A control mechanism that allows or denies traffic that wants to pass through a port.
  • Authentication server: Validates the credentials of the supplicant that is trying to access the network or resource.

During a port-based network access control interaction, a LAN port adopts one of two roles: authenticator or supplicant. In the role of authenticator, a LAN port enforces authentication before it allows user access to the services that can be accessed through that port. In the role of supplicant, a LAN port requests access to the services that can be accessed through the authenticator’s port. An authentication server, which can be either a separate entity or colocated with the authenticator, checks the supplicant’s credentials on behalf of the authenticator. The authentication server then responds to the authenticator, indicating whether the supplicant is authorized to access the authenticator’s services.

The authenticator’s port-based network access control defines two logical access points to the LAN through one physical LAN port. The first logical access point, the uncontrolled port, allows data exchange between the authenticator and other computers on the LAN, regardless of the computer’s authorization state. The second logical access point, the controlled port, allows data exchange between an authenticated LAN user and the authenticator.

In a wireless network environment, the supplicant typically is a network host. The authenticator could be the wireless network switch or AP. The role of authentication server would be played by a Remote Authentication Dial-In User Service (RADIUS).

RADIUS is a protocol that allows a single server to become responsible for all remote-access authentication, authorization, and auditing (or accounting) services.

RADIUS functions as a client/server system. The remote user dials in to the remote access server, which acts as a RADIUS client, or network access server (NAS), and connects to a RADIUS server. The RADIUS server performs authentication, authorization, and auditing (or accounting) functions and returns the information to the RADIUS client (which is a remote-access server running RADIUS client software). The connection is either established or rejected based on the information received.

Temporal Key Integrity Protocol

As mentioned previously, WEP lacked security. Temporal Key Integrity Protocol (TKIP) was designed to address the shortcomings of the WEP security protocol. TKIP is an encryption protocol defined in IEEE 802.11i. TKIP was designed not only to increase security but also to use existing hardware, making it easy to upgrade to TKIP encryption.

TKIP is built on the original WEP security standard but enhances it by “wrapping” additional code at both the end and the beginning of the data packet. This code modifies the code for additional security. Because TKIP is based on WEP, it too uses the RC4 stream encryption method. But unlike WEP, TKIP encrypts each data packet with a stronger encryption key than is available with regular WEP.

TKIP provides increased security for data communications, but it is far from the final solution. TKIP provides strong encryption for home users and nonsensitive data. However, it may not provide the level of security necessary to protect corporate or more sensitive data while in transmission.

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