How can I effectively prevent data exfiltration by malicious employees?

It's crucial to realize that TLS decryption might not solve everything. If a user encrypts their data before TLS, you won't have meaningful content to analyze. Plus, enabling TLS decryption can cause issues with other web services, making it not feasible for general use. Disabling USB ports and scanning email attachments is a more straightforward approach to prevent data theft.

Implementing Data Loss Prevention (DLP) solutions is a solid approach. If you're using something like Microsoft Defender, it's capable of blocking uploads to specific websites, which can be configured to prevent potential data exfiltration. This might require using Edge for full functionality. Plus, it can restrict copying and pasting data, which adds another layer of security. Even if someone tries to manually enter data, the DLP could still flag those uploads.

It's a tough call, really. You can create an intranet that doesn't allow any internet access to help keep sensitive data in-house, but that might not be practical for everyone. Ultimately, building a trustworthy company culture where employees feel valued could help, but unfortunately, trust alone isn’t a foolproof method. Actual DLP strategies are essential for this.