: ArcGIS 10.5 was originally released in December 2016. Most versions from this era are now in the "Mature" or "Retired" support phases, meaning they no longer receive routine security patches or technical support.
If you need to download ArcGIS software, you should only use official channels to ensure the installer is secure and genuine: ArcGIS Enterprise Life Cycle - Esri Support ESRI ArcGIS Server Enterprise 10.5 Free Download
Below is a report on how to legitimately access, license, and download ArcGIS Enterprise software. Software Status and Licensing : ArcGIS 10
: At version 10.5, the product formerly known as "ArcGIS for Server" was renamed to ArcGIS Enterprise . ESRI ArcGIS Server Enterprise 10.5 Free Download