Researchers at Trend Micro have observed samples of the Netwalker ransomware that are not compiled but written in PowerShell and executed directly in memory without storing the ransomware binary onto the disk. Known as “fileless” malware, this technique allows the ransomware to evade detections and use tools already installed on the machines to launch attacks. Fileless malware also utilizes reflective Dynamic-Link Library (DLL) injection. This allows a DLL to be injected into targeted processes from memory instead of a disk and is stealthier than normal DLL injection because it does not use the normal Windows loader as most DLLs do. This avoids the need for registering the DLL as a loaded module and allows the malware to evade DLL load monitoring tools. The PowerShell script that is used hides under various layers of encryption, obfuscation and encoding to also evade static detection techniques.
By Anthony Zampino Introduction Leading up to the most recent Russian invasion of Ukraine in