While performing an attack it is key for an attack to stay undetected for as long as possible and we notice that every major hack happens because incident response is not started up soon enough. This is why it is so important to have proper logging and monitoring in place with an alerting system setup.

ImpactsAlmost all major attacks start by checking what vulnerabilities are possible. If we do not log and monitor this sufficiently, it has been shown that the likelihood of an attack increases drastically. We need to ensure to take action at the first sight of a probe but we can only do this if we monitor and alert our already proficient logs.
Security weaknessOften when an attack happens the logging that is done does not contain all the details that are required to debug this major event. A strategy that many have taken is to first execute a pentest or run a vulnerability scanner in aggressive mode (This allows the scanner to execute full on attacks) and to investigate the logs afterwards.