Which action should a security team take when investigating a potential Trojan horse incident?

When investigating a potential Trojan horse incident, examining e-mails for suspicious links is a critical action for the security team. Trojan horses often infiltrate systems via malicious links or attachments in e-mails. Analyzing e-mails can provide valuable information about how the Trojan may have entered the system, the sender's identity, and whether there are additional targets or compromised systems associated with the incident. This step is essential in understanding the threat landscape and taking measures to prevent further infections.

The other options are less effective in addressing the immediate investigation of a Trojan horse incident. Ignoring the incident, even if no visible damage is apparent, poses a significant risk, as these malware types can operate stealthily and cause harm over time. Updating all software immediately may be a necessary maintenance step but does not directly aid in investigating how the Trojan was delivered or understanding its behavior. Focusing solely on newly downloaded files may overlook other vectors of infection, such as files already present on the system that could have been exploited or modified by the Trojan. Therefore, examining e-mails provides a comprehensive and proactive approach to the investigation.