Which of the following is a common tool used for network security monitoring?

A common tool used for network security monitoring is indeed firewalls and intrusion detection systems. Firewalls serve as barriers that control and monitor incoming and outgoing network traffic based on predetermined security rules, helping to prevent unauthorized access to or from a private network. Intrusion detection systems (IDS) supplement this by continuously monitoring network traffic for suspicious activities or policy violations. When malicious activity is detected, these systems can alert administrators, enabling them to take appropriate measures to mitigate risk.

Together, firewalls and intrusion detection systems form a critical part of a comprehensive network security strategy, actively working to protect organizational data from potentially harmful threats. The combination of both tools ensures a layered security approach, where firewalls manage access control while intrusion detection systems focus on identifying and responding to threats in real-time.