A wave of cyberattacks driven by artificial intelligence is coming, and companies have a narrow window to defend themselves.

That was the message of an open letter published on Thursday by OpenAI and more than 100 major technology companies and others. The letter said that A.I. labs should provide their best A.I. models to organizations like hospitals and infrastructure providers so they can prepare and that governments should help coordinate and fund cyberdefense.

The letter’s signatories included Google, Microsoft and OpenAI’s archrival, Anthropic, as well as cybersecurity and financial firms such as CrowdStrike, a company known for investigating cyberattacks against the Democratic National Committee in 2015 and 2016, and credit card providers like Visa and Mastercard.

“The companies and public services our communities depend on — from hospitals to water treatment plants to the infrastructure that powers the internet — are at risk,” the letter said. “A.I. enabled cyber attacks will become far more widespread and sophisticated as models around the world become increasingly capable.”

The letter signaled that major companies are becoming increasingly fearful of the hacking abilities of A.I. and whether A.I. labs can fully control the behavior of their models. In recent public statements, some A.I. labs have called on governments to regulate them to slow the pace of A.I. development so the technology’s abilities do not outstrip their capacity to control it.

The letter follows a spate of cyberattacks from A.I. models, with the models in some cases going rogue. Last month, OpenAI’s A.I. models broke out of a testing environment and hacked Hugging Face, an online repository of open A.I. models. Hugging Face said it faced a barrage of attacks that no human attacker could manage, with OpenAI’s bots taking more than 17,000 actions, like sending attack commands and exploiting vulnerabilities.

Since the attack, OpenAI said that it was increasing its security to prevent its models from breaking out during testing.

Anthropic also recently revealed that one of its A.I. models broke into the systems of three outside organizations during a test. Meta has said its A.I. models have done something similar.

Some tech executives are becoming increasingly concerned about the power of artificial intelligence. Bill Gates, the billionaire co-founder of Microsoft, said in an interview this month with The New York Times that addressing these risks should be “the world’s top priority.”

In Thursday’s letter, the companies argued that making A.I. widely available for defense could help fix “weaknesses that have accumulated for years.”

“If we act decisively, we can use the defenders’ window to make our digital world much more secure,” the letter said.

(The Times has sued OpenAI and Microsoft, claiming copyright infringement of news content related to A.I. systems. The two companies have denied those claims.)