The criminals claim to have been inside the company's networks for more than a month before posting internal data (screenshot below) on a dark web site on Friday.

REvil, which is also known as Sodinokibi, can only be used to attack systems running Microsoft's Windows operating system.

In a statement to ransomware specialist site Bleeping Computer, Brown-Forman said it had managed to prevent encryption of its data, as it had noticed the attack and taken remedial steps.

According to Wikipedia, Brown-Forman, based in Louisville, Kentucky, manufactures well-known brands such as Jack Daniel's, Early Times, Old Forester, Woodford Reserve, GlenDronach, BenRiach, Glenglassaugh, Finlandia, Herradura, Korbel, and Chambord around the world.

The company formerly owned two other popular brands, Southern Comfort and Tuaca, before selling them off in 2016.

The last figure given for Brown-Forman's global revenue by Wikipedia dates from 2016; at that time, Brown-Forman was pulling in US$3.08 billion (A$4.28 billion).

Contacted for comment, a Brown-Forman spokesperson told iTWire: "Brown-Forman was the victim of a cyber security attack. Our quick actions upon discovering the attack prevented our systems from being encrypted.

"Unfortunately, we believe some information, including employee data, was impacted. We are working closely with law enforcement, as well as world class third-party data security experts, to mitigate and resolve this situation as soon as possible. There are no active negotiations.

"Protecting the privacy and security of personal information is extremely important to us. The company deeply regrets any inconvenience or concern this may cause. Keeping information secure is a priority for Brown-Forman. We know this news comes at an already challenging time and may be disconcerting given the uncertainty of the situation.

"We encourage everyone to stay vigilant and alert to potential cybersecurity threats, including avoiding phishing attempts and malicious websites."