A silent install is the installation of a software program that requires no user interaction. It is a convenient way to streamline the installation process of a desktop application. Silent installs are performed by many legitimate software programs, but they are also used by malware and PUPs to hide the installation process from the user.
A typical installer has several parameters that instruct the installer how to run. Examples include where the program should be installed, if a shortcut should be placed on desktop, and if additional components should be installed. In a non-silent or "attended installation," the user is prompted to select or confirm these options during the installation process. In a silent install, these items are selected automatically and the installer runs from start to finish without requiring any user input.
Silent installs are useful for simple programs that have limited installation options. They are also helpful for installing software on several machines at once. For example, a network administrator may prefer to distribute a software program via a silent installer to ensure all users within the network have the same installation settings. Even though silent installers run without any user interaction, legitimate programs typically require you to manually initiate the installation process.
While silent installations are used for many good reasons, some programs, such as spyware and adware use silent installers to run without your knowledge. These types of programs may even run without you initiating the installation process. They may be tacked on to another installer or executed by a malicious file, such as virus.