What is an Insider Threat?
Insider threats, told as a story about a castle whose wall, bell, and dog all face outward — while someone with a key opens the door from within.
Our castle guards the outside well. The wall, the bell, the dog all face out.The wall, the guard dog, the guard room. A thief outside can't get in.
But the door opens from inside — on purpose, by mistake, or by someone who already left.The maid takes gold and opens it on purpose. The cook drops the roster by accident. The carpenter quit but never returned the key. None of them ring the bell.
An insider threat is someone who opens the door from inside.The wall faces out, but the person with the key is already inside. On purpose, by mistake, or after leaving — when a key opens the door, the bell stays quiet.
When it's not like usual, the bell rings from inside too.The maid only visits the kitchen by day. So — the vault at midnight, key used 20 times? Compare the log with the usual, and odd behaviour from inside shows up.
A castle that guards the inside too is a truly strong castle.Give key rings only as needed, let the doorkeeper catch the red stamp, spot odd behaviour in the log, and have the roster office take keys back on the way out.
Insider threat = someone inside the castle with a key opening the door on purpose, by mistake, or after leaving. The wall and the bell only face out, so you need eyes on the inside too.
A threat from someone with legitimate access — an employee or contractor — who harms the organization maliciously, negligently, or through access that outlived their job. Countered with least privilege, DLP, behaviour analytics (UEBA), and offboarding.
When grown-ups say it
- Insider threat
- Someone inside who has a key. The wall, bell, and dog all face out, so this person walks right past.
- Malicious · Negligent · Departed
- The maid, the cook, the carpenter. Opening a door for gold, dropping the roster, keeping a key. All three come from inside.
- UEBA (User and Entity Behavior Analytics)
- The maid's usual vs. tonight. If the kitchen-by-day person is at the vault at midnight, ring the bell. → the guard room's big screen
- Separation of duties
- The vault takes two keys at once. Split big jobs so one person alone can't do them: the one who counts the gold isn't the one who sends it.
- Offboarding
- Take the key back the day they leave. The day the carpenter quits, cross him off the roster and collect the key. → the roster office
- DLP (Data Loss Prevention)
- Red-stamped papers never leave. Even if the cook carries it out by mistake, the doorkeeper catches it. → the red-stamped paper
- Least privilege
- Kitchen folk get only the kitchen key. Fewer keys, fewer doors to open. → a key ring per hat, the master key in the vault
- Audit log
- Who opened which door, and when. Odd behaviour from inside shows up only in the log. → the one-line log book