SWIFT, the global financial messaging network that banks use to move billions of dollars every day, warned on Thursday of a second malware attack similar to the one that led to February's $81 million cyberheist at the Bangladesh central bank.

The second case targeted a commercial bank, SWIFT spokeswoman Natasha de Teran said, without naming it.

SWIFT said in a statement that the attackers exhibited a "deep and sophisticated knowledge of specific operational controls" at targeted banks and may have been aided by "malicious insiders or cyber attacks, or a combination of both."

The organization, a Belgian co-operative owned by member banks, said that forensic experts believe the second case showed that the Bangladesh heist "was not a single occurrence, but part of a wider and highly adaptive campaign targeting banks."

News of a second case comes as law enforcement authorities in Bangladesh and elsewhere investigate the February cyber theft from the Bangladesh central bank account at the New York Federal Reserve Bank. SWIFT has acknowledged that that scheme involved alteringSWIFT software to hide evidence of fraudulent transfers, but that its core messaging system was not harmed.

SWIFT had previously acknowledged that the Bangladesh Bank attack was not an isolated incident but one of a number of recent criminal schemes aimed at its messaging platform, which is used by 11,000 financial institutions globally.

It said that its messaging system was not compromised with the second case, which involved targeting a PDF reader used by the bank to check its statement messages.