Microsoft Web Servers Targeted By Hacker ‘Praying Mantis’: Cybersecurity Firm Cybersecurity firm Sygnia said that the threat actor’s campaign focused on Windows IIS servers, and has involved a ‘custom malware framework tailor-made for IIS servers.’ By Wade Tyler Millward August 02, 2021, 05:42 PM EDT A new threat actor is targeting Microsoft Windows web servers, suggesting that users should patch .NET deserialization vulnerabilities and look for suspicious activity on web-facing Microsoft Internet Information Services servers, according to cybersecurity technology and services provider Sygnia. Tel Aviv-based Sygnia recently issued a report stating that researchers found “an advanced memory-resident attack commonly associated with nation-state actors.”