<P> The IEEE set up a dedicated task group to create a replacement security solution, 802.11 i (previously this work was handled as part of a broader 802.11 e effort to enhance the MAC layer). The Wi - Fi Alliance announced an interim specification called Wi - Fi Protected Access (WPA) based on a subset of the then current IEEE 802.11 i draft . These started to appear in products in mid-2003 . IEEE 802.11 i (also known as WPA2) itself was ratified in June 2004, and uses the Advanced Encryption Standard AES, instead of RC4, which was used in WEP . The modern recommended encryption for the home / consumer space is WPA2 (AES Pre-Shared Key), and for the enterprise space is WPA2 along with a RADIUS authentication server (or another type of authentication server) and a strong authentication method such as EAP - TLS . </P> <P> In January 2005, the IEEE set up yet another task group "w" to protect management and broadcast frames, which previously were sent unsecured . Its standard was published in 2009 . </P> <P> In December 2011, a security flaw was revealed that affects some wireless routers with a specific implementation of the optional Wi - Fi Protected Setup (WPS) feature . While WPS is not a part of 802.11, the flaw allows an attacker within the range of the wireless router to recover the WPS PIN and, with it, the router's 802.11 i password in a few hours . </P> <P> In late 2014, Apple announced that its iOS 8 mobile operating system would scramble MAC addresses during the pre-association stage to thwart retail footfall tracking made possible by the regular transmission of uniquely identifiable probe requests . </P>

Which of the following wireless ieee standards operates exclusively in the 2.4ghz radio frequency