T1546.016Detection written

Installer Packages

Privilege Escalation · PersistenceLinux, macOS, Windows

Where this stands

One published detection covers this technique. Every one is unverified — no rule on Siemphony has been executed against real telemetry.

Unexpected child process spawned by msiexec.exeby Siemphony

What the technique is

Adversaries may establish persistence and elevate privileges by using an installer to trigger the execution of malicious content. Installer packages are OS specific and contain the resources an operating system needs to install applications on a system. Installer packages can include scripts that run prior to installation as well as after installation is complete. Installer scripts may inherit elevated permissions when executed. Developers often use these scripts to prepare the environment for installation, check requirements, download dependencies, and remove files after installation. Using legitimate applications, adversaries have distributed applications with modified installer scripts to execute malicious content. When a user installs the application, they may be required to grant administrative permissions to allow the installation. At the end of the installation process of the legitimate application, content such as macOS postinstall scripts can be executed with the inherited elevated permissions. Adversaries can use these scripts to execute a malicious executable or install other malicious components (such as a Launch Daemon) with the elevated permissions. Depending on the distribution, Linux versions of package installer scripts are sometimes called maintainer scripts or post installation scripts. […]

Read it on attack.mitre.org

What MITRE says you would watch

AN0938
Correlation of package install event with execution of postinstall scripts containing unknown binaries or abnormal CLI usage. Look for /usr/sbin/installer execution followed by child processes originating from postinstall script.
AN0939
Detection of maintainer scripts (e.g., postinst, preinst) being modified or executed during dpkg or rpm operations. Watch for script content that spawns additional processes or writes outside package scope.
AN0940
Detection of msiexec.exe running installer packages that result in anomalous process creation. Look for unexpected binaries executed by msiexec or custom action DLLs in the temp directory.