A network allowlist is a security policy that permits outbound or inbound connections only to approved domains, hostnames, or IP addresses. Everything else is blocked by default. It is a practical form of network filtering used to reduce exposure and keep systems from talking to untrusted destinations.
In cyber security, allowlists matter because they can limit data exfiltration, block command-and-control traffic, and prevent tools or workloads from reaching arbitrary internet services. They are common in sandboxed environments, agentic AI systems, and tightly controlled enterprise networks where only specific APIs, package mirrors, or internal services should be reachable. An allowlist is not a complete defense on its own: if a malicious or misbehaving process is allowed to reach a trusted service, abuse can still occur. For that reason, teams pair allowlists with logging, identity controls, and human approval for sensitive actions.