In the context of incident response, unsuccessful scans and probes are typically considered a low severity level. This is because they often indicate an attempted reconnaissance or mapping of systems rather than a successful compromise or disruption of services. While they should be monitored and analyzed to improve defenses and detect patterns of malicious activity, they do not usually signify an immediate threat to the integrity, availability, or confidentiality of systems.
References: The classification of unsuccessful scans and probes as low severity is consistent with standard practices in incident response and is supported by various cybersecurity frameworks and guidelines, including those from the EC-Council's Certified Network Defender (CND) program.