DNS Security Extensions (DNSSEC) are a set of Internet Engineering Task Force (IETF) standards created to address vulnerabilities in the Domain Name System (DNS) and protect it from online threats. The purpose of DNSSEC is to increase the security of the Internet as a whole by addressing DNS security weaknesses. Essentially, DNSSEC adds authentication to DNS to make the system more secure.
The Domain Name System manages Internet navigation by locating domain names and mapping them to IP addresses. DNS, as originally designed, has no means of determining whether domain name data comes from the authorized domain owner or has been forged. This security weakness leaves the system vulnerable to a number of attacks, such as DNS cache poisoning, for example.
In a DNS cache poisoning attack, an intruder replaces a valid IP address cached in a DNS table with a rogue address. Requests for the valid address are redirected accordingly, and malware -- such as a worm, spyware or browser hijacker -- may be downloaded to the user's computer from the rogue location. DNSSEC employs cryptographic keys and digital signatures to ensure that lookup data is correct and that connections are to legitimate servers.
The core elements of DNSSEC were specified in three IETF Requests for Comments published in March 2005: RFC 4033 - DNS Security Introduction and Requirements, RFC 4034 - Resource Records for the DNS Security Extensions, and RFC 4035 - Protocol Modifications for the DNS Security Extensions.
DNSSEC implementation is somewhat complex and is on a voluntary basis. As a result, adoption has been slow. In the United States, the federal government has mandated DNSSEC implementation for government networks. The National Institute of Standards and Technology (NIST) and the General Services Administration (GSA) have implemented the standards within the top level dot.gov domain. However, most individual agencies have yet to meet the mandate for second-level domains.
DNSSEC is offered as a managed service; DNSSEC appliances that automate the process are also available from some vendors.