DNS Security

DNS Security Module Quick DNS Refresher

1

What is DNS? •  The Domain Name System (DNS) associates names;; most various information with domain names importantly, it serves as the "phone "phone book" book" for the Internet by translating human-readable human-readable computer hostnames, e.g. www.example.com hostnames, www.example.com,, into addresses,, e.g. 208.77.188.166 208.77.188.166,, which IP addresses king equipment needs to deliver networking networ information. •  A DNS also stores other information such as the list of mail servers that servers that accept email for email for a given domain. By providing a worldwide keyword keyword-based -based redirection service, the Domain Name System is an essential component of contemporary Internet  Internet  use. –  Source Wikipedia 2

Hierarchical Name Space www.cs.stanford.edu root

org

wisc

edu

net

com

stanford

ucb

cs

uk

cmu

ca

mit

ee

www= 192.168.20.1 3

DNS Server Functions/Roles •  Zone (Domain): A DNS zone is a portion of the global Domain Name System (DNS) System (DNS) namespace  namespace  for which administrative responsibility has been delegated. Zone = apricot.net

Zone Administrator  

Zone Files

Master DNS Server

Recursive DNS Server Client

Dynamic Updates (DHCP & AAA)

Slave DNS Server (s)

4

DNS Server Functions/Roles •  Zone Master (Primary): The authoritative server for a zone (domain). The Zone Master contains one or more zone files for which the DNS is authoritative. Other DNS Servers can automatically transfer zone files. Zone Administrator  

Zone Files

Master DNS Server

Recursive DNS Server Client

Dynamic Updates (DHCP & AAA)

Slave DNS Server (s)

5