Audit-log integrity

The activity log is append-only, and every entry stores a SHA-256 hash of its contents chained to the hash of the entry before it. Changing, deleting or reordering any entry breaks the chain from that point.

Running the check

On Platform → Activity, choose Verify integrity. The service recomputes the hash of every entry and checks each link:

• N events verified: the whole chain is intact.
• N problem(s) from event #ID: entries starting at that ID don’t verify. Each problem is either hash mismatch (row was modified) or chain broken (row missing or reordered).

Every check is itself recorded as admin.audit_verified with the result.

If the check fails

Treat it as a security incident. Don’t try to “fix” the table. Preserve a copy of the database, find out who had owner or superuser access to the audit database, and compare with your backups to see what changed.

The check reads the whole log, so on a large log it can take a while. How the chain and the database protections work is described in Database and the write-only audit log.