Which of the following programs can be used to detect stealth port scans performed by a malicious hacker? Each correct answer represents a complete solution. Choose all that apply.

portsentry is a port scan detection daemon that monitors for connection attempts on unused ports and can trigger automated responses such as blocking or alerting when scan patterns are detected.

nmap is an active network scanning and enumeration tool used to perform port scans - it generates the scan traffic rather than detecting it, making it the opposite of what is needed here.

scanlogd is a dedicated syslog-based tool that detects TCP port scanning attempts by analyzing the frequency and distribution of incoming connection attempts across ports.

libnids is a network intrusion detection library that implements IP defragmentation and TCP stream reassembly, enabling applications built on it to identify port scan patterns and other anomalous traffic behaviors.