FastViewer is Android malware associated with Kimsuky and distributed as repackaged APKs that embed malicious code inside legitimate applications. Earlier samples impersonated Hancom Office Viewer, while a later variant retained the package name, application name, icon, and selected features of another legitimate mobile application. The original FastViewer downloaded and loaded FastSpy, a remote-control module based on the open-source AndroSpy tool. Variants observed since at least July 2023 combine FastViewer and FastSpy functionality directly and no longer require a separate malware download.