In the 1990s, a major Wall Street brokerage came under SEC investigation for allegedly deleting customer emails. This incident created SEC Rule 17a-4(f), mandating "WORM (Write Once Read Many)" storage—once recorded, no one can erase or modify. What once required optical disks or special tape, AWS implemented via Backup Vault Lock's Compliance mode—activate it and even AWS's root user cannot delete backups.