OS Resource Exhaustion via TCP Connection Flood

This rule detects a TCP connection flood, specifically looking for a high rate of TCP SYN packets (indicated by the 'flags:S' keyword) directed towards a single destination IP address within a short timeframe. A threshold of 500 SYN packets within 5 seconds to the same destination triggers the alert. This behavior is characteristic of a Denial of Service (DoS) attack, aiming to exhaust the target's resources by overwhelming it with connection requests.