An executable file contains instructions that an operating system or interpreter can run. It may be a complete application, an installer, a command-line tool, or a script. Executable does not mean malicious, but running an untrusted file can give its code access to your account and data.
Common executable formats
- Windows:
.exe,.com,.scr, and command or script files such as.bat,.cmd, and.ps1. An.msipackage can install executable software. - macOS: application bundles, Mach-O binaries, packages, and scripts.
- Linux and Unix: ELF binaries and scripts. Execute permissions and the file header matter more than a filename extension.
Documents can also contain active content such as macros, and shortcuts can launch commands. An ordinary-looking icon or filename is therefore not proof that a file is safe.
Why double extensions are risky
Windows may hide known extensions by default. A file displayed as invoice.pdf can actually be named invoice.pdf.exe. Turn on file-extension display and inspect the full name before opening an unexpected download or attachment.
Checks before running a file
- Download software from its official publisher or a trusted application store.
- Confirm the filename and version match what the publisher documents.
- On Windows, open Properties and check whether the Digital Signatures tab shows a valid signature from the expected company.
- Compare a published cryptographic hash when the vendor provides one. A matching hash confirms the file is identical to that release, but does not independently prove the release is safe.
- Scan the file with current security software. Treat an unexpected request for administrator rights as a reason to stop and verify.
If the file may be malicious
Do not run it again. Quarantine it, note where it came from, and perform a full system scan. If it already ran, review startup items, browser changes, and account activity. Change important credentials from a clean device if the file could have stolen data.