When Zero Trust Isn’t Enough: How Insiders Breach Secure Systems

Zero Trust security is designed to stop threats by verifying every user, device, and action with no exceptions. But what happens when the threat comes from inside? Despite strong Zero Trust frameworks, insiders continue to find ways to bypass controls and breach sensitive systems. Here’s how they do it and what organizations are learning from these failures.

Common Weaknesses Exploited by Insiders

• Overprivileged Access: Admins and trusted employees often have more access than necessary.
• Misconfigured Policies: Shared drives, cloud apps, and legacy systems left outside Zero Trust controls.
• Lack of Monitoring: No alerts for abnormal behavior like bulk downloads or off-hours access.
• Human Factors: Social engineering, bribery, and poor offboarding practices open doors.

Finance: Data Theft in Trusted Networks

• Morgan Stanley: A financial adviser downloaded 730,000 client records over 3 years. Zero Trust failed due to lack of internal monitoring and overly broad access.
• Desjardins: An employee exfiltrated data from a shared drive not covered by Zero Trust policies. The breach went unnoticed for 26 months.

Lesson: Zero Trust must include internal monitoring and strict data segmentation, even for “trusted” employees.

Healthcare: IoT and Identity Gaps

• Pharma IP Theft: A researcher downloaded 12,000 confidential files from cloud storage before resigning. Cloud apps weren’t monitored.
• Hospital IoT Sabotage: An insider accessed an HVAC system via weak credentials, exposing patients to risk.
• Stradis Healthcare: A fired VP used a secret account to sabotage shipping records. Identity governance failed.

Lesson: Zero Trust must extend to cloud, IoT, and identity management. Offboarding processes need to be airtight.

Government: Clearance Isn’t Enough

• Edward Snowden: Used admin privileges and social engineering to access and leak classified NSA data. Lack of segmentation and monitoring enabled the breach.
• Jack Teixeira: A junior IT specialist printed and leaked classified Pentagon documents. Excessive access and poor physical controls were exploited.

Lesson: Zero Trust must be enforced even for cleared personnel. Behavioral analytics and compartmentalization are critical.

Tech: IP Theft and Admin Tool Abuse

• Yahoo: A scientist stole 570,000 pages of source code before leaving. No alerts flagged the massive download.
• Tesla: Employees leaked 100GB of internal data after leaving. Legitimate access was abused.
• Twitter: Hackers bribed an insider to hijack accounts via admin tools. Overly broad internal access was the weak link.

Lesson: Monitor internal data movement, limit admin privileges, and enforce Zero Trust for internal tools not just external access.

Final Takeaway

Zero Trust is powerful, but not foolproof. Insiders can still exploit gaps in identity, monitoring, and policy enforcement. To truly defend against insider threats, organizations must:

• Enforce least privilege and monitor behavior continuously.
• Extend Zero Trust to cloud, IoT, and legacy systems.
• Audit access regularly and tighten offboarding procedures.
• Educate employees and build insider threat programs.

Zero Trust is a mindset, not just a toolset. Trust no one. Verify everything. Watch everyone.