An application protocol based intrusion detection system (APIDS) is like a security guard for your network. It helps to protect your network from intruders or attackers who might try to hack in and access your files or data. APIDS monitors the traffic that comes in and out of your network and looks for suspicious activity. It uses the application protocols that your network uses, like https and FTP, to look for patterns that could mean someone is trying to break in. If it finds anything suspicious, it will alert you so that you can take action to protect your network.