Athreat actor has successfully breached the network firewall without being detected by the ids system. what condition describes the lack of alert?

false negative

Explanation:

A false negative is a dangerous state in which the IDS (Intrusion Detection System) assumes the activity as acceptable in which the activity is actually an attack occurred on the system.

That means, the Intrusion Detection System has failed to catch the attack. This is the most dangerous state, as the systems were compromised and the network or cyber security people were unable to find the attack.

More generally, there are two types of Intrusion Detection Systems ( IDS ). Network based IDSs ( NIDS ) and Host based IDSs ( HIDS ).