D3 provides several levels of security, including:
File retrieval and update lock codes.
Separation of user and account, each with their own unique passwords.
Port logon control. After three unsuccessful log on attempts, the port is disabled to prevent further attempts. To re-enable the port, press any key, other than ENTER, followed by pressing ENTER twice. This is primarily in cases where someone is using a dial-up line and gets line noise, which could be interpreted as an invalid an log on.