If you must use Sierra 10.12.6 for work, keep it offline, use Firefox ESR, and never log into iCloud or work email. Otherwise, treat this download as a bridge to upgrade your hardware. Your data is worth more than a few saved seconds of boot time.
It was the first version to drop the "OS X" moniker in favor of "macOS". Stable Legacy Hardware: For machines like the Late 2009 MacBook Mid 2010 Mac Pro work download macos sierra 1012 6
The internet is littered with fake DMG files and malware-ridden torrents claiming to be "macOS Sierra 10.12.6." Cybercriminals frequently inject ransomware into old OS installers. If you must use Sierra 10