Insider Threats: When the Risk Is Already Inside the Building

The 30-second explanation

An insider threat comes from someone who already holds the keys: an employee, contractor or partner with real, working access. They might be careless, tricked, or simply upset about something. Either way, the security controls built to stop outsiders do nothing to stop them.

How it works

1. 1

   1. Legitimate access

   The person is trusted, badged, and genuinely allowed in.

2. 2

   2. Trigger

   A mistake, outside pressure, a grievance, or a hijacked account sets things off.

3. 3

   3. Action

   Data ends up exposed, copied, or otherwise misused.

4. 4

   4. Detection

   Someone notices behaviour that doesn't match this person's usual pattern.

Most insider incidents turn out to be accidents: a file shared with the wrong person, a laptop left on a train, a link clicked without thinking. A smaller share are deliberate, and they tend to cluster around a resignation, a dispute, or financial pressure. Because the access itself is legitimate, technical defences built to keep intruders out are largely useless here. What's left is behaviour: unusual data volumes, odd hours, access to files that have nothing to do with someone's actual job. A programme that works pairs tight access hygiene with monitoring that staff know exists and trust to be applied fairly.

Real-world example

How to spot it

• An unusual volume of data movement

  Large downloads or copies that sit well outside a person's normal pattern.

• Access that strays outside the role

  Browsing systems or folders that have nothing to do with the actual job.

• Repeated odd-hours activity

  Out-of-hours access that keeps happening with no obvious reason behind it.

• Work data heading to personal accounts

  Files or emails sent to a personal address or personal cloud storage.

What to do

1. 1Give people only the access their role needs, and remove it promptly the moment a role changes or someone leaves.
2. 2Monitor sensitive data movement openly, in a way staff already know about, and handle alerts fairly and privately.
3. 3Make it easy to report a mistake quickly and without blame, so a small error doesn't quietly turn into a breach.