Many "free ISO" sites bundle malware or modify system files.
Apple never officially distributed El Capitan as an . The official installer came as a .app bundle inside a disk image ( .dmg ) or downloaded directly from the Mac App Store. ISOs you find on third-party sites are often homemade conversions — sometimes fine, sometimes risky. Mac Os X 10.11 El Capitan Iso Download
You must use Safari to open these links for proper redirection. Creating an ISO from the Installer Many "free ISO" sites bundle malware or modify system files