Access Control ensures that resources are only granted to those users who are entitled to them.
Access Control List (ACL)
A mechanism that implements access control for a system resource by listing the identities of the system entities that are permitted to access the resource.
Authentication
Authentication is the process of confirming the correctness of the claimed identity.
Botnet
A botnet is a large number of compromised computers that are used to create and send spam or viruses or flood a network with messages as a denial of service attack.