IEEE 802.11 access points deployed in shopping malls, university campuses, crowded streets, airports, and many other locations provide ubiquitous Internet access to millions of stations. However, these hot spots are vulnerable to Denial-of-Service (DoS) attacks due to the broadcast nature of wireless communication. It does not require specialized hardware or particularly high level of experience to render 802.11 networks inoperable through DoS attacks. Standard off-the-shelf equipment is sufficient for a malicious station to disrupt the service between access points and stations. In this paper we present a systematic survey of DoS attacks, which exploits MAC and physical layer vulnerabilities of 802.11 networks. Available countermeasures against DoS attacks are discussed and compared. Future research directions and open issues are also discussed. (C) 2008 Elsevier B.V. All rights reserved.