India’s City Union Bank said on Sunday that “cyber criminals” had hacked its systems and transferred nearly $2 million through three unauthorized remittances to lenders overseas via the SWIFT financial platform.

The comments come after the small private lender on Saturday had disclosed it had discovered the three “fraudulent remittances”, which were sent via correspondent banks to accounts in Dubai, Turkey and China. Chief Executive Officer N. Kamakodi called it a “conspiracy” involving multiple countries, and added the lender was still investigating how it had happened. “This is basically a cyber attack by international cyber criminals,” he told. 

SWIFT, the global messaging system used to move trillions of dollars each day, warned banks that the threat of digital heists is on the rise as hackers use increasingly sophisticated tools and techniques to launch new attacks.

Brussels-based SWIFT has been urging banks to bolster security of computers used to transfer money since Bangladesh Bank lost $81 million in a February 2016 cyber heist that targeted central bank computers used to move funds. The new warning provided detail on some new techniques being used by the hackers. “Adversaries have advanced their knowledge,” SWIFT said.

Hackers released documents and files on Friday that cybersecurity experts said indicated the U.S. National Security Agency had accessed the SWIFT interbank messaging system, allowing it to monitor money flows among some Middle Eastern and Latin American banks.

The release included computer code that could be adapted by criminals to break into SWIFT servers and monitor messaging activity, said Shane Shook, a cyber security consultant who has helped banks investigate breaches of their SWIFT systems. The documents and files were released by a group calling themselves The Shadow Brokers.

Cyber attacks targeting the global bank transfer system have succeeded in stealing funds since February’s heist of $81 million from the Bangladesh central bank as hackers have become more sophisticated in their tactics, according to a SWIFT official and a previously undisclosed letter the organization sent to banks worldwide.

The messaging network in a Nov. 2 letter warned banks of the escalating threat to their systems, according to the SWIFT letter. The attacks and new hacking tactics underscore the continuing vulnerability of the SWIFT messaging network, which handles trillions of dollars in fund transfers daily.

A few months after hackers broke into Bangladesh's central bank and came close to getting away with $1 billion, researchers have uncovered evidence that a separate hacking group is targeting the same payment network.

The researchers, from security firm Symantec, said that they recently found new tools that target users of SWIFT, a payment network banks use to transfer payments that are sometimes in the range of hundreds of millions of dollars. The malicious tools monitor SWIFT messages sent to infected computers for International Bank Account Numbers or other keywords relating to specific transactions. 

SWIFT, the global financial messaging system, disclosed new hacking attacks on its member banks as it pressured them to comply with security procedures instituted after February's high-profile $81 million heist at Bangladesh Bank.

SWIFT said that new cyber-theft attempts have surfaced since June, when it last updated customers on a string of attacks discovered after the attack on the Bangladesh central bank. The disclosure suggests that cyber thieves may have ramped up their efforts following the Bangladesh Bank heist, and that they specifically targeted banks with lax security procedures for SWIFT-enabled transfers.

A Ukrainian bank has become the latest victim of the widespread cyber attack on global banking and financial sector by hackers who target the backbone of the world financial system, SWIFT. Hackers have reportedly stolen $10 Million from an unnamed bank in Ukraine.

Swift or the Society for Worldwide Interbank Financial Telecommunication is the global banking messaging system responsible for managing Billions of dollars in money transfers each day between financial institutions worldwide. The ISACA branch in Ukraine disclosed that some unknown hackers were able to compromise the bank's security in similar way they hacked Bangladesh central bank.

Bangladesh's central bank was vulnerable to hackers because it did not have a firewall and used second-hand, $10 switches to network computers connected to the SWIFT global payment network, an investigator into one of the world's biggest cyber heists said.

The shortcomings made it easier for hackers to break into the Bangladesh Bank system earlier this year and attempt to siphon off nearly $1 billion using the bank's SWIFT credentials, said Mohammad Shah Alam, head of the Forensic Training Institute of the Bangladesh police's criminal investigation department. "It could be difficult to hack if there was a firewall," Alam said in an interview.