If you need to reinstall macOS High Sierra on older Mac hardware (late 2009 to mid-2017), you should avoid random torrent sites or unknown third-party hosting services. A "verified" DMG means the file has not been tampered with, contains a valid code signature from Apple, and matches the original checksum.
shasum /path/to/your/Installer.dmg
The safest way to get a verified copy is directly from Apple. Although you cannot find High Sierra by simply searching the App Store on a modern Mac, Apple provides direct links through their support pages. download mac os high sierra 10136 dmg verified
Once you have the installer app in your Applications folder, you can create a bootable installer on a USB drive (which functions like a bootable DMG) using this Terminal command: If you need to reinstall macOS High Sierra
Note: This downloads the full installer, which is effectively a wrapper around the DMG contents needed for installation. Although you cannot find High Sierra by simply