Security researchers have discovered hundreds of copies of a Chinese-made AI hacking tool publicly exposed to the internet for anyone to access, potentially allowing outsiders to launch cyberattacks against unsuspecting targets.

The hacking software, called Artex, is an open-source autonomous penetration testing tool, meaning software that automatically probes computer systems for weaknesses, and it’s been linked to several cyberattacks since its public release in July. As open-source software, it’s free for anyone to download and run on their own servers, making it a popular tool for those who cannot access Anthropic or OpenAI’s most advanced cybersecurity AI models for discovering security vulnerabilities. Microsoft has previously described Artex as a system of AI agents that can conduct cyberattacks “from reconnaissance through data exfiltration with little needed human interaction.”

In a blog post, cybersecurity firm Censys, which scans the internet for exposed or vulnerable systems, said that it identified more than 800 distinct deployments of Artex that were accessible from the web without needing a password to.

Silas Cutler, principal security researcher at Censys who wrote the blog post, said that not every instance of Artex is operated maliciously and many are used for authorized testers. But it’s unclear why hundreds of these Artex systems are exposed to the web, as the software does not require them to be accessible from the internet.

The findings underscore how even powerful hacking tools can be misconfigured to be publicly accessible by anyone, increasing the chance that someone will find and misuse them. The publicly accessible systems also expose attack tools, such as implants (hidden malicious software) used to compromise and maintain persistent access to a victim’s network.

Security companies have linked the use of Artex to several broad-scale cyberattacks, including against the Korean finance industry in September. Cybersecurity giant CrowdStrike attributed the attacks to a Chinese-speaking hacker who used an Artex instance in the attacks, in part because the hacker had left an “open directory” hosting the system. Censys said that its data showed the Artex instance in question had been publicly exposed for months, and appeared to contain more attack data that extended “well beyond South Korean banks,” including payment and gaming companies.

Artex was also used in an attack on IT support giant ConnectWise earlier in October, which allowed Chinese-linked hackers to spy on thousands of organizations whose data and files are hosted in Microsoft’s cloud. Microsoft, which has visibility into the attack, said in a blog post that the hackers used Artex to break into customer’s cloud environments and steal their data at such speed that defenders had “little time to detect and respond.”Many of the attacks linked to Artex involved exploiting simple vulnerabilities, such as guessing weak or known passwords, and a lack of multi-factor authentication.

The findings show that simple vulnerabilities, including misconfigurations, can expose both the attacker and their targets.

Artex has since announced it would go closed-source, effectively limiting further releases for paid customers. There are still dozens of copies of Artex’s code available on code-sharing sites that can still be used in active attacks.