A supply chain attack which targeted Mastra, an open-source typescript for building AI-powered applications and agents, was the work of North Korean hackers, cybersecurity researchers have said.

The attribution was made on June 19 by Microsoft Defender Security Research Team and Microsoft Threat Intelligence.

The technology giant assessed with “high confidence” that the activity is attributable to Sapphire Sleet, a North Korean state actor that primarily targets the financial sector.

Microsoft made the attribution after it observed the infrastructure and post-compromise TTPs used in the Mastra campaign were consistent with previously documented Sapphire Sleet activity.

Sapphire Sleet is the name designated to the group by Microsoft. Other threat intelligence investigators track the North Korean hacking group as APT38, BlueNoroff, Stardust Chollima and TA444.

Over 140 packages across Mastra scopes on the npm registry, the largest open-source database of JavaScript code sharing in the world, were affected by Sapphie Sleet’s “large-scale npm supply chain attack,” according to Microsoft. By targeting this, the aim of the attackers was to compromise developers.

The source of the compromise was the takeover of a npm maintainer account, which had its publishing privileges abused to publish poisoned instances of Mastra code with easy-day-js, a malicious dependency.

Read more: AI Adoption Creates New Opportunities for Attackers to Distribute Malware, Microsoft Warns

This poisoned instance was used to disabled Transport Layer Security (TLS) certificate verification, contact an attacker-controlled command-and-control (C2) server, which then delivered a malware payload, which could be deployed on Windows, MacOS and Linux systems.

The aim of this was twofold. First, like many cyber-attacks attributed to North Korea, the campaign targeted cryptocurrency wallets. The malware searched for the existence of 166 cryptocurrency wallet browser-extension IDs, including MetaMask, Phantom, Coinbase Wallet, Binance Wallet, TronLink, and others, with the intent to steal from them.

The malware could also gather information on browser history, as well as perform reconnaissance on the infected machine, gathering information on the hostname, architecture, platform, user ID, installed applications and running processes.

Microsoft has not detailed how the privileged accounts were taken over to poison packages, but the blog post noted that Sapphire Sleet has a history of social engineering attacks harnessing LinkedIn against victims in the financial, blockchain and cryptocurrency sectors.

To help protect against this campaign, Microsoft has issued the following advice:

• Review dependency trees for direct or transitive usage of affected @mastra packages at the compromised versions listed above
• Check for the presence of easy-day-js in node_modules/ or package-lock.json files across your projects and CI/CD environments
• Pin known-good package versions where possible. For mastra, version 1.13.0 and earlier are unaffected. Foz @mastra/core, version 1.42.0 and earlier are unaffected