A group that has taken credit for leaking NSA cyber spying tools — including those used in the recent WannaCrypt global ransomware attack — has threatened in a blog it is believed to have authored to release more recent code to enable hackers to break into the world's most widely used computers, software and phones.

Using trademark garbled English, the apparent ShadowBrokers communique promised that, starting next month, it will begin releasing tools on a monthly basis to anyone willing to pay for access to some of the tech world's biggest commercial secrets.

It also threatened to dump data from banks using the SWIFT international money transfer network and from Russian, Chinese, Iranian or North Korean nuclear and missile programs, without providing further details. "More details in June," it promised.

"ShadowBrokers are back" tweeted Matthieu Suiche, a French hacker and security researcher who has tracked the group. Among the notable claims, he said, was that it had newer exploits for Microsoft's Window 10 operating system dating from after 2013.

The NSA used the Microsoft flaw to build a hacking tool codenamed EternalBlue that ended up in the hands of a mysterious group called the Shadow Brokers, which then published that and other such tools online.