“Big Four” professional services firm Deloitte yesterday disclosed that hackers had successfully breached the organization's email system last fall and may have had access to its emails up until the breach was discovered in March of this year.

Deloitte did not respond to requests for comment, but confirmed the cyberattack to reporters for The Guardian and Gizmodo. In statements provided to each of these publications, Deloitte said that “very few” clients had been “impacted,” though it did not disclose the depth of said impacts, and that each client had been notified. Deloitte additionally noted that it had contacted both government authorities and regulators and had retained law firm Hogan Lovells to review the incident.

Jon Neiditz, partner at Kilpatrick Townsend & Stockton and co-leader of Kilpatrick's cybersecurity, privacy and data governance practice, noted that Deloitte's admission that hackers had specifically breached its email system reflects a breach of its “crown jewels,” or its most valuable asset.