What it means
DNS gives applications a way to look up information associated with a name. Address records commonly connect a website name to an Internet Protocol address, while other record types support functions such as email routing. A recursive resolver finds answers on a client's behalf; authoritative servers publish the records for a domain.
Answers can be cached for a limited time, so a record change may not appear everywhere immediately. Security work involves both protecting the ability to change records and understanding what the observed answer means. A correct DNS answer does not prove that a website is safe, and DNS alone does not authorize access to an application.
AN ILLUSTRATIVE SCENARIO
A charity website move
A charity moves its donation website to a new hosting service. Its administrator updates the domain's address records, but some visitors still reach the old service because their resolvers retain cached answers. The administrator compares the authoritative records with answers from several resolvers and checks the record's time to live, or cache duration. Meanwhile, the team protects the domain management account and verifies that both the old and new endpoints behave safely during the transition.
Put it to work
- Identify who manages domain registration, authoritative DNS, and the resolver used by your devices; these may be different services and owners.
- Record important names, record types, intended destinations, and cache durations before a planned change; protect the accounts that can edit them.
- Check authoritative and resolver answers after the change, then verify the actual application and its certificate at the intended destination.
dig example.com A
dig example.com AAAAHow to check your work
Compare a documented expected record with an authoritative answer and a client lookup. Confirm that the application reached through that name is the intended service and that change ownership is clear.
Connect the ideas
- IP address
A numeric locator used to deliver packets to a host on a network.
- HTTP
The application protocol that names methods, paths, headers, and bodies for web requests.
- TLS
A protocol that encrypts and integrity-protects an application conversation and checks a certificate for a name.
- Asset
Anything whose disclosure, alteration, destruction, or downtime would harm a person or organization.