Which component of the IT Security Model is attacked with masquerade?

A masquerade attack involves an attacker pretending to be an authorized user of a system, thus compromising the authentication component of the IT security model. Authentication ensures that the individuals accessing the system are who they claim to be. By masquerading as a legitimate user, an attacker can bypass this security measure and gain unauthorized access to the system.References:

William Stallings, "Security in Computing".