Bob finished a C programming course and created a small C application to monitor the network traffic and produce alerts when any origin sends "many" IP packets, based on the average number of…

A true IDS - whether signature-based or behavior-based - must detect indicators of intrusion, not simply flag high-volume traffic from a source. Bob's tool measures raw packet counts relative to an average and fires alerts on threshold breaches, which is the core function of packet-rate network monitoring tools, not intrusion detection. Legitimate high-traffic sources such as backup servers or streaming clients would trigger the same alerts, demonstrating the tool lacks the intrusion-specific correlation needed to be an IDS.

A signature-based IDS detects threats by matching traffic against a database of known attack patterns or signatures, a capability Bob's tool entirely lacks.

A hybrid IDS combines both signature-based and anomaly-based detection engines, which is far beyond the single-metric threshold alerting Bob implemented.

A behavior-based IDS builds a multi-dimensional statistical baseline of normal system and network behavior and correlates deviations specifically tied to intrusion indicators, whereas Bob's tool only tracks a single metric - packet count per source.