A sudden spike in network traffic can be a significant indicator of potential security incidents, such as a DDoS (Distributed Denial of Service) attack or data exfiltration. Such unusual activity may suggest that a threat actor is attempting to gain unauthorized access to the network or is already conducting malicious activities. Immediate investigation is essential to ensure the integrity and security of the network, as it may help in identifying, mitigating, and responding to ongoing attacks before they escalate or cause substantial damage.
The other scenarios, while they might warrant attention, generally do not necessitate immediate action. For example, installing an unapproved application could indicate a policy violation, but it might not immediately threaten network security. A missed scheduled maintenance can signify operational issues but doesn’t typically imply an ongoing security threat. Unsuccessful login attempts could suggest credential theft attempts or brute force attacks, still, they might not be grounds for immediate investigation without additional context such as the user's role and behavior patterns.