what a canary token is and how it works?

Question

what a canary token is and how it works?

In: 554

Answer 1

Apart from the already mentioned uses of the term:

* A ‘tripwire’ to indicate a document / data was accessed.
* A notice indicating that a site has never been served a NSL or similar (more often called a *warrant canary*).

There is also the computer coding canaries:

* added at the end (most common location) of an in memory data structure, when the code path retrieves the data structure if the canary has changed, something corrupted the data structure (bad code, malicious code, failing hardware). A useful technique to guard against buffer overflows.
* As initial value of some variable – if it has not been changed from the canary then some configuration path / setup has not been run. A common use of this “ChangeMe” if a user hasn’t changed the value then either use a default setting or generate an error (and exit).