Credit check firm Equifax reportedly discovered hackers had breached its systems months before stealing the personal information of 143 million customers.

The company, which has kept a low profile since it announced the hack earlier this month, was targeted by the same cyber criminals five months before the major data breach.

In what has been described as an unrelated attack, hackers accessed Equifax's computer systems in March, according to Bloomberg.

No information was stolen in the initial attack, Equifax said, but it will draw further attention to the embattled company, which has suffered severe reputational damage including a criminal investigation.

It has emerged Equifax hired security company Mandiant back in March following the initial breach, which it believed was resolved, according to Bloomberg. It then called Mandiant back on July 29 following the second breach in which the personal and financial information of millions of customers was stolen.

Equifax has come under fire in the wake of the attack for its failure to support customers and its lack of transparency.