Countering DNS Amplification Attacks Based on Analysis of Outgoing Traffic

Domain name system (DNS) amplification distributed denial of service (DDoS) attacks are one of the popular types of intrusions that involve accessing DNS servers on behalf of the victim. In this case, the size of the response is many times greater than the size of the request, in which the source of the request is substituted for the address of the victim. This paper presents an original method for countering DNS amplification DDoS attacks. The novelty of our approach lies in the analysis of outgoing traffic from the victim's server. DNS servers used for amplification attacks are easily detected in Internet control message protocol (ICMP) packet headers (type 3, code 3) in outgoing traffic. ICMP packets of this type are generated when accessing closed user datagram protocol (UDP) ports of the victim, which are randomly assigned by the Saddam attack tool. To prevent such attacks, we used a Linux utility and a software-defined network (SDN) module that we previously developed to protect against port scanning. The Linux utility showed the highest efficiency of 99.8%, i.e., only two attack packets out of a thousand reached the victim server.