A North Korean hacking group deployed new and improved malware against an engineering firm in an attempt to steal sensitive technology with military applications, security researchers said on Wednesday.

According to analysts with Symantec, the attack likely began with the intrusion of a public-facing virtual desktop server using the Log4j exploit, one of the most serious zero-day vulnerabilities discovered last year.

Symantec said in a blog post on Wednesday that Stonefly, a DPRK-backed hacking group sometimes referred to as Silent Chollima, was behind the attack.

“Virtually all of the technologies it appears