Final answer:
Azure Active Directory Identity Protection is the service that uses machine learning to detect irregularities in user behavior and notify users of potentially harmful access attempts.
Step-by-step explanation:
The Azure service that detects anomalies in account activities and notifies you of potential harmful attempts to access your account is Azure Active Directory Identity Protection. This service utilizes machine learning to detect irregularities in user behavior and evaluate potential threats, providing a risk assessment for each detected issue and recommending appropriate actions to mitigate the risk. It can detect issues like atypical travel, unfamiliar sign-in properties, leaked credentials, and sign-ins from infected devices.