Dhaka, March 17 (IANS): Hackers, who stole $81 million from Bangladesh's central bank in February, had hacked a key printer that was used to print payment receipts, due to which the theft went undetected for some time, the reported on Thursday.

The hacking, which resulted in the resignation and sacking of some top management members of the Bangladesh Bank, began on February 4 at the end of the working week at the bank, when hackers, who apparently managed to get hold of the bank's credentials for its account with the Federal Reserve Bank of New York (Fed), issued instructions for several transactions, The Daily Star reported.

Details of the probe revealed a bank employee who visited the office on February 5, a holiday, found the printer connected to the SWIFT financial messaging company was not functioning and tried to fix the problem but in vain.

He visited again the following day, also a holiday, and attempted to fix the issue but the software connected to the terminal did not respond, instead displayed a message saying "a file is missing or changed".

When he tried to manually print the confirmation, the printing system did not respond.

Bank sources told EFE news, the bank became aware on February 6 that five of the 35 transfers to accounts in several Asian countries, amounting to $951 million had been validated, resulting in a capital flight of $101 million.

It then tried to contact SWIFT and the Fed to revoke the payments, but failed as it was a bank holiday in the US.

Later, between February 8-9, it sent payment cancellation instructions to recipient banks, managing to recover $20 million from funds transferred to accounts in Sri Lanka, but not the $81 million deposited into accounts in the Philippines.

The greatest bank cyber heist in Bangladesh's history prompted the resignation of Bangladesh Bank chief Atiur Rahman on Tuesday. Former finance ministry secretary Fazle Kabir was named as his replacement on Wednesday.