The EC-Council Incident Handler (ECIH) curriculum explains that insider data exfiltration frequently occurs through legitimate channels such as HTTPS to bypass traditional firewall rules. When encrypted traffic is not inspected, sensitive data can be transmitted without detection.

Data Loss Prevention (DLP) tools monitor, detect, and block unauthorized transmission of sensitive information across endpoints, networks, and cloud services. DLP solutions can inspect encrypted traffic (when integrated with SSL/TLS inspection mechanisms) and enforce policies that prevent confidential data from leaving the organization.

The absence of deep packet inspection allowed encrypted HTTPS traffic to evade detection. Implementing DLP would provide content-aware monitoring and policy-based enforcement, reducing insider exfiltration risk.

Option A (biometric authentication) controls access, not outbound data flows. Option C (secure coding) relates to software development security. Option D (USB blocking) addresses removable media exfiltration, not encrypted network traffic.

Therefore, implementing Data Loss Prevention (DLP) tools is the appropriate eradication control.