The Domain Name System (DNS) is a critical part of the Internet infrastructure. Virtually every Internet application depends on some form of DNS data, yet access to and the reliability of that data aren't assured. DNS attacks and abuses, meanwhile, are increasingly common and sophisticated. Part of the problem is that security wasn't a major goal of the original DNS design. The DNS community has been aware of security issues for decades, but only now are solutions ready for wide-scale deployment. Motivated by both its importance and recent enhancements to strengthen its security, this issue of IEEE Security and Privacy looks at the challenges in securing the DNS.