What are the possible security risks associated with deploying and using WiMax?
WiMax is the much-anticipated broadband wireless access mechanism for delivering high-speed connectivity over long distances, making it attractive to Internet and telecommunications service providers. Designed by the IEEE 802.16 committee, WiMax was developed after the security failures that plagued early IEEE 802.11 networks. Recognising the importance of security, the 802.16 working groups designed several mechanisms to protect the service provider from theft of service, and to protect the customer from unauthorised information disclosure.
Authentication A fundamental principle in 802.16 networks is that each subscriber station (SS) must have an X.509 certificate that will uniquely identify the subscriber. The use of X.509 certificates makes it difficult for an attacker to spoof the identity of legitimate subscribers, providing ample protection against theft of service. A fundamental flaw in the authentication mechanism used by WiMax's privacy and key management (PKM) protocol is the lack of base station (BS) or service provider authentication. This makes WiMax networks susceptible to man-in-the-middle attacks, exposing subscribers to various confidentiality and availability attacks. The 802.16e amendment added support for the Extensible Authentication Protocol (EAP) to WiMax networks. Support for EAP protocols is currently optional for service providers.
Encryption With the 802.16e amendment, support for the AES cipher is available, providing strong support for confidentiality of data traffic. Like the 802.11 specification, management frames are not encrypted, allowing an attacker to collect information about subscribers in the area and other potentially sensitive network characteristics.
Availability WiMax deployments will use licensed RF spectrum, giving them some measure of protection from unintentional interference. It is reasonably simple, however, for an attacker to use readily available tools to jam the spectrum for all planned WiMax deployments. In addition to physical layer denial of service attacks, an attacker can use legacy management frames to forcibly disconnect legitimate stations. This is similar to the deauthenticate flood attacks used against 802.11 networks.
Despite good intentions for WiMax security, there are several potential attacks open to adversaries, including:
- Rogue base stations
- DoS attacks
- Man-in-the-middle attacks
- Network manipulation with spoofed management frames
The real test of WiMax security will come when providers begin wide-scale network deployments, and researchers and attackers have access to commodity CPE equipment. Other attacks including WiMax protocol fuzzing may enable attackers to further manipulate BSs or SSs. Until then, the security of WiMax is limited to speculation.
Joshua Wright is the senior security researcher for Aruba Networks, an editorial board member of the Wireless Vulnerabilities and Exploits project (WVE)and a senior instructor for the SANS Institute. This article appeared in Network World.