0140-3664/$ see front matter 2012 Elsevier B.V. A http://dx.doi.org/10.1016/j.comcom.2012.04.008 ⇑ Corresponding author. Tel.: +32 484143830. E-mail addresses: Hakem.Beitollahi@esat.kuleuve Deconinck@esat.kuleuven.be (G. Deconinck). This paper reviews and analyzes well-known countermeasures against distributed denial of service (DDoS) attacks. This paper provides an in-depth analysis of each countermeasure and enumerates strengths and challenges of each technique. If it is possible, the paper designs a countermeasure against each defense mechanism from the attacker’s point of view. We believe that this survey is the most complete survey that analyzes the most cited DDoS defense techniques in detail. We expect that this survey will assist the potential victims to choose suitable countermeasures against DDoS attacks based on the analysis presented here and as well as the capabilities that they have to implement the techniques. The analysis done in this paper provides a great opportunity for both academic and industrial researchers to improve the state of the art countermeasures against DDoS attacks. 2012 Elsevier B.V. All rights reserved.