Threat hunting is a proactive security activity focused on identifying hidden or undetected threats within an environment, even when no alerts or indicators have been triggered. According to CompTIA Security+ SY0-701, threat hunting assumes that attackers may already be present and actively evading traditional security controls such as SIEMs, IDS/IPS, or endpoint protection tools.

Threat hunting involves manually analyzing logs, endpoint telemetry, network traffic, and behavioral patterns to uncover anomalies that automated systems may miss. This aligns directly with the scenario, where the analyst has a suspicion of malicious actors but no alerts confirming activity. Threat hunting helps identify advanced persistent threats (APTs), living-off-the-land techniques, credential misuse, and lateral movement that may not generate immediate alerts.

Digital forensics (B) is typically performed after an incident has been confirmed. Vulnerability scanning (C) identifies weaknesses but does not detect active attackers. E-discovery (D) is a legal process for collecting electronically stored information and is not used for threat detection.

Because the analyst is proactively searching for hidden threats without existing alerts, the correct action is A: Threat hunting.