O(1) is ________.

Used to control how users enter data into a field in order to maintain consistency with data entry

a. Input Mask b. Registered value c. Format Mask

Once an attacker gains remote control access over a system, they want to retain this illicit access. Some attackers will block the system update service to prevent new updates from fixing vulnerabilities that are needed to maintain remote control over the compromised system. To prevent such a compromised system from allowing the attacker to access resources on the network, what security mechanism should be implemented?

A. Network access control B. A Web security gateway C. Complex password authentication D. Intrusion detection system