How do alleged secret societies stay hidden?

The first correction: almost no private organisation is actually hidden. Freemasonry owns buildings and files annual reports. Service clubs advertise. Private clubs have street addresses.

What is protected is the membership list and the content of internal discussion — the same protection a therapist's client list enjoys.

The main mechanism is not enforcement but culture. Members who value the confidentiality extended to them extend it in return. Groups that gossip lose the members worth having, and the norm sustains itself.

This is why private organisations that survive tend to be the ones where discretion is a genuine value rather than a rule.

Structures where no single person knows everything appear in intelligence work, corporate deals and some fraternal orders. Individually harmless facts held separately are hard to assemble from outside.

It is also a limit on capability: a compartmentalised organisation cannot execute an ambitious coordinated plan, which undercuts the conspiracies attributed to such structures.

People talk. They confide in partners, boast when drunk, resign angrily, write memoirs and die leaving papers. Every large secret in modern history has eventually surfaced, usually within a generation.

The practical ceiling on secrecy is small numbers and low stakes. Scale either up and it leaks.

Identity, and nothing else. The principles, rules and application process are published precisely so that anyone can read them before applying.

A group that hid its principles would be asking for a commitment nobody could evaluate. That would fail its own honesty test.