Methods, systems, and computer programs encoded on computer storage medium, for identifying a first user access event that failed authentication at the first computing device; creating a transaction block of a distributed ledger based on the first user access event; determining that data indicating the first user access event is not included by the distributed ledger, and in response, adding the transaction block to a temporal vector space of the distributed ledger; sharing, to each other computing device of the local network, the transaction block, wherein each of the others computing devices of the local network updates a local copy of the distributed ledger to include the transaction block in the temporal vector space.