A file leak is the alleged release or theft of data files from an organization. In cyber security, the phrase usually refers to claims that documents, databases, archives, or internal records were copied out and then published, sold, or used for extortion.
It matters because a leak can expose sensitive information, create privacy and regulatory risk, and increase pressure on victims to pay. In ransomware and extortion campaigns, attackers often advertise a file leak with file counts, sample screenshots, or directory names to make the claim look credible. Defenders should treat such claims as unverified until they confirm data exfiltration through logs, endpoint evidence, backup reviews, and network monitoring. A public file leak claim is not proof of compromise, but it is a strong signal to investigate quickly.