DNS & Domain Security Terms

A DNS record that maps a hostname to an IPv4 address. The most fundamental DNS record type.

A database of IP addresses or domain names known to send spam, host malware, or engage in phishing. Mail servers and browsers query blacklists to block or flag suspicious traffic.

Canonical Name record — maps a hostname to another hostname rather than an IP address. Used for aliases and pointing subdomains at external services.

DomainKeys Identified Mail — an email authentication standard that uses public-key cryptography to sign outgoing messages, allowing receivers to verify the email came from the claimed domain and wasn't altered in transit.

Domain-based Message Authentication, Reporting & Conformance — the policy layer of email authentication that ties SPF and DKIM to the From: header and specifies what to do when messages fail.

Domain Name System — the internet's distributed database that translates human-readable domain names (example.com) into IP addresses and other machine-readable data.

Hypertext Transfer Protocol Secure — HTTP with TLS encryption. HTTPS encrypts data between browser and server and authenticates the server's identity via an SSL/TLS certificate.

Mail Exchange record — a DNS record that specifies the mail servers responsible for receiving email for a domain, with priority values to control which server is tried first.

A server that stores DNS records for a domain and answers DNS queries. Your domain's nameservers are the authoritative source for all DNS data about your domain.

A cyberattack that uses deceptive emails, websites, or messages to trick victims into revealing credentials, financial data, or installing malware. Most attacks impersonate trusted brands via spoofed domains or emails.

Sender Policy Framework — a DNS TXT record that lists which mail servers are authorized to send email for a domain. Receiving servers check the sender's IP against this list.

Secure Sockets Layer / Transport Layer Security — cryptographic protocols that encrypt data in transit between a client (browser) and server. TLS is the modern version; SSL is deprecated but the name persists.

Time to Live — a value in DNS records (in seconds) that controls how long resolvers and browsers cache the record before fetching a fresh copy from the authoritative nameserver.

A DNS record type that stores arbitrary text strings. Originally for human-readable notes, now primarily used to publish SPF, DKIM, DMARC, and domain verification data.