The company should use Amazon GuardDuty, as it is specifically designed to offer continuous monitoring and detect unusual network traffic, malicious attacks, and other potential threats, making it the best fit for this scenario. On the other hand, AWS Security Hub aggregates and displays security findings from across the environment, but it does not offer detection capabilities on its own. Amazon Inspector is used for application security assessments and AWS Shield focuses on DDoS protection, which is not specifically related to monitoring network traffic and detecting threats in the way described by the scenario.