Microsoft Internet Information Services (IIS) is a web server software package designed for Windows Server. Organizations commonly use Microsoft IIS servers to host websites, files, and other content on the web. Threat actors increasingly target these Internet-facing resources as low-hanging fruit for finding and exploiting vulnerabilities that facilitate access to IT environments.
Recently, a slew of activity by the advanced persistent threat (APT) group Lazarus has focused on finding vulnerable Microsoft IIS servers and infecting them with malware or using them to distribute malicious code. This article describes the details of the malware attacks and offers actionable suggestions for protecting Microsoft IIS servers against them.