File Picture: Kacper Pempel/Reuters

JOHANNESBURG - Global accountancy firm Deloitte has been hit by a sophisticated hack that resulted in a breach of confidential information and plans from some of its biggest clients, Britain’s Guardian newspaper said yesterday.

Deloitte - one of the big four professional services providers - confirmed it had been hit by a hack, but it said only a small number of clients had been affected. The firm discovered the hack in March, according to the Guardian, but the attackers could have breached its systems as long ago as October or November last year.

The attack was believed to have been focused on the US operations of the company, which provides auditing, tax advice and consultancy to multinationals and governments worldwide.

“In response to a cyber incident, Deloitte implemented its comprehensive security protocol and began an intensive and thorough review,” a spokesperson told the newspaper. “As part of the review, Deloitte has been in contact with the very few clients impacted and notified governmental authorities.”