Warren Buffett sees cyber attacks as a bigger threat to humanity than nuclear weapons.

“I’m very pessimistic on weapons of mass destruction generally although I don’t think that nuclear probably is quite as likely as either primarily biological and maybe cyber,” Buffett said during Berkshire Hathaway’s annual shareholders’ meeting on Saturday.

“I don’t know that much about cyber, but I do think that’s the number one problem with mankind.”

Last year, Buffett said CNBC — cyber, nuclear, biological and chemical attacks — posed a major threat to the economic well-being of Berkshire shareholders.

“If [a nuclear attack] ever happens, there’ll be more to worry about than the price of Berkshire,” Buffett noted.

In 2015, Berkshire made a bet that could profit from increased cyber breaches. Berkshire Hathaway Specialty Insurance launched two insurance policies that cover cyber liability and the costs incurred to respond to a data breach or threat.

Similarly, AIG launched a product earlier this year that covers expenses arising from online bullying and extortion, according to Fortune.