Access Control Lists (ACLs) are a fundamental element of network security, allowing organizations to define and enforce access permissions for network resources. ACLs can be used to secure company resources both internally and externally, improve performance and manageability, and reduce the risk of spoofing and denial of service attacks. There are four types of ACLs: Standard, Extended, Dynamic, and Reflexive, each with its own strengths and limitations. To set up effective ACLs, organizations should use ACLs inside and outside network interfaces, pay attention to the order of ACL entries, set rules for groups rather than users, document everything, use ACL management tools, and combine Role-Based Access Control (RBAC) with ACLs. Twingate offers a modern approach to access control that makes ACL management more efficient by implementing software-defined perimeters and Zero Trust Network Access principles.