Legitimate credentials are valid usernames, passwords, tokens, or keys that belong to a real account. In cyber security, the danger is not whether the login works, but who is using it and for what purpose. If attackers steal or misuse these credentials, they can enter systems as if they were trusted users, often bypassing edge defenses and basic access checks.
This is why legitimate credentials are central to many modern intrusions. They let attackers blend in, use normal remote tools, access shared services, and move laterally without triggering obvious alarms. Defenders reduce this risk with multi-factor authentication, least privilege, privileged access controls, and strong logging. Deception tools such as decoys can also help, because unexpected use of a valid account may expose suspicious internal activity.