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A Record Lookup

The Address (A) record is the most fundamental DNS record type, used to map a domain name to an IPv4 address.

RFC: RFC 1035
TYPE: Resource Record
PROTOCOL: IPv4

What is A Record Lookup?

An A record (Address Record) is a DNS record that points a domain name (like example.com) to an IP address (like 192.0.2.1) of the server hosting the domain. It is essential for web traffic as it allows browsers to find the physical location of a website using human-readable names.

How it Works

When you type a URL into your browser, a DNS query is sent. The resolver checks for the A record of that domain. If found, it returns the IPv4 address, allowing your browser to initiate a TCP/IP connection to the server.

Key Use Cases

Pointing a root domain to a web server.

Creating subdomains (e.g., blog.example.com) that point to different servers.

Setting up multiple A records for round-robin load balancing.

Advanced Details

Multiple A records can exist for a single domain, which is a common technique for basic load balancing. If one server is down, the resolver may try the next IP address in the list.

Cybersecurity Pros & Cons

Security Advantages
  • Enables quick IP correlation with threat intelligence feeds to identify malicious hosting infrastructure.
  • Multiple A records (round-robin) reduce single-point-of-failure risk during DDoS attacks.
  • Real-time A record lookup can detect fast-flux DNS used by botnets that rapidly cycle IP addresses.
  • Helps security teams map an attacker's server footprint by resolving all associated domains.
Security Limitations
  • Without DNSSEC, A records can be poisoned via cache injection attacks, redirecting users to malicious IPs.
  • Shared hosting means one blacklisted IP affects all legitimate domains on the same server.
  • Attackers can use bulletproof hosting with legitimate-looking A records to evade IP-based blocklists.
  • IPv4 exhaustion means IPs are frequently recycled, making historical IP-domain correlation unreliable.
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