Security is a topic on everyone's mind. What can we do to proactively protect our computers from threats and vulnerabilities. One of the features used to protect your computer is a firewall. A firewall acts as a barrier for unauthorized communication to your computer. With a VPC, this firewall is called a Network Access Control List (NACL). In this lesson, we discuss NACLs and describe how to create rules to allow and deny traffic through the NACL.