IP blocking is a technique that prevents the connection between a server/website and certain IP addresses or ranges of addresses. Which of the following tools use this technique? Each correct answer…

SSHGuard monitors logs for brute-force attempts against SSH and a narrow set of other services, and while it can invoke firewall actions, it is scoped to specific services rather than functioning as a general-purpose IP blocking framework.

Portsentry listens on unused TCP/UDP ports, detects port scan attempts in real time, and automatically blocks the scanning host by updating firewall rules or the /etc/hosts.deny file, making IP blocking its primary function.

OpenSSL is a cryptographic toolkit that implements SSL/TLS and manages certificates; it has no capability to monitor network traffic or block IP addresses.

Nmap is a network discovery and port scanning tool used to probe hosts and enumerate services; it contains no mechanism to block or deny IP addresses.

Fail2Ban monitors system log files for repeated failed authentication attempts or other attack patterns and dynamically adds firewall rules (such as iptables DROP rules) to block the offending IP address for a configurable duration.