The new gatekeeper is for mountain lion, mavericks, yosemite, el capitan, sierra and high sierra.
Technically gatekeeper dates back to lion 10.7.5 in its GUI form. Prior to that there was the spct1 command in 10.7.3 and 10.7.4. And prior to that there was File Quarantine in Leopard and Snow Leopard.
This new version of gatekeeper however has not been released for lion.
Also I said before the El Capitan Security Update 2018-003 at https://support.apple.com/kb/DL1967?viewlocale=en_US&locale=en_US gives you build 15G21012 whereas the one from the mac app store gives you 15G21013.
So if you want the standalone installers for build 15G21013 they are here instead (install in this order - last one requires a restart):
Full Bundle Update: http://swcdn.apple.com/content/down...r8xlta8sfkdwkm2cxjk069ri/FullBundleUpdate.pkg
Firmware Update: http://swcdn.apple.com/content/down...mgr8xlta8sfkdwkm2cxjk069ri/FirmwareUpdate.pkg
Security Update 2018-003: http://swcdn.apple.com/content/down...sfkdwkm2cxjk069ri/SecUpd2018-003ElCapitan.pkg
@tywebb13
Thank you, Thank you, Thank you
I am learning from you a lot!
I will try to install El Capitan in the order you suggest
Any Xprotect update?
Thanks
Camelia