Hitachi Payments Services yesterday accepted its systems were compromised by a sophisticated malware in mid-2016, that led to one of the biggest cyber security breaches in country with 3.2 million cards affected, and a scare over security of card-based transactions.

The National Payments Corporation of India (NPCI) had said over 600 customers had reported losses of at least Rs 1.3 crore due to the breach.

The company, a wholly-owned subsidiary of the Japanese Hitachi, made the acknowledgement following the receipt of final assessment report from payments and information security audit firm SISA Information Security, and said it "regrets" the inconvenience caused.