Definition
Allowlisting, also known as whitelisting, is a security practice where only explicitly approved items are permitted to access a system or network. Instead of blocking known bad actors, this approach focuses on permitting only known good entities. In practice, an allowlist functions as a gatekeeper, granting access only to applications, IP addresses, or users that are pre-approved. This is crucial for preventing unauthorized access and mitigating the risk of malware infections by limiting the attack surface. For instance, a company might implement an allowlist for software applications, ensuring only company approved programs can run on employee workstations. This differs from blocklisting, which identifies and prevents access by known malicious entities. Allowlisting is a key concept tested on CompTIA Security+, CySA+, and CISSP certifications.