An MSI package is a Windows Installer file format used to install, repair, or remove software on Windows systems. It provides a structured installation workflow with metadata, files, and actions that the operating system can execute during setup.
In cyber security, MSI packages matter because attackers can abuse this trusted installation path to deliver payloads while appearing to perform normal software deployment. A malicious MSI may launch scripts, drop additional files, or run helper processes as part of installation, which can help it evade basic suspicion. Defenders look for unusual installer behavior, such as unexpected network activity, strange child processes, or installers that do far more than deploy software. Monitoring process lineage and validating the source and purpose of MSI files helps expose misuse.