A network intrusion detection system (or NIDS) is like an alarm system for your computer that can detect suspicious activity and alert you when it finds something wrong. It uses a set of rules to look for patterns in network traffic that could indicate malicious activity. For example, if an individual is trying to access certain files or websites, the NIDS can sound the alarm and alert you to stop the intruder. It can also be used to detect malware or viruses on your computer. NIDS can help keep your computer and data safe from hackers and other malicious attackers.