Hackers have stolen $10 million from an unnamed Ukrainian bank, according to an independent IT monitoring organisation.

The Kyiv branch of ISACA, the Information Systems Audit and Control Association, reported this week that the theft had occurred via the SWIFT international banking system, the organisation responsible for managing money transfers between financial institutions worldwide.

ISACA announced the theft after being hired by a Ukrainian bank to investigate. It did not name which bank had hired it to conduct the investigation.

“At the current moment, dozens of banks (mostly in Ukraine and Russia) have been compromised, from which has been stolen hundreds of millions of dollars,” ISACA said in a release.

The organisation said that such hacks usually take months to complete. After breaking into a financial institution’s internal networks, hackers will take time to study the bank’s internal processes and controls. Then, using the knowledge and access they have gathered, the hackers will begin to submit fraudulent money orders to webs of offshore companies, allowing them to siphon off millions of dollars.

ISACA said that the hackers likely used publicly available information and tools to commit the theft. The organisation also added that the same hack had likely spread to other banks in the Ukrainian financial system.

“Banks now are not sharing such information at all and are afraid of publicity,” said Aleksey Yankovsky, head of ISACA’s Kyiv division.

The announcement follows months of controversy surrounding the security of SWIFT. In February, hackers managed to steal more than $100 million from the Bangladesh Central Bank’s account in the New York Federal Reserve through an attack made via the SWIFT network. That incident led to calls for renewed attention to the system’s safety, as well as criminal investigations by Bangladesh, the Philippines, and the United States.

Ukraine’s banking sector has also come under repeated criticism for a failure to implement Western-style security standards, as well as for a slew of other allegedly bad practices.