Can you limit share functionality?

[Deleted]

As an organization we limit who has access to what on specific sites and control the permissions using O365 groups. It seems that the share allows employees to get around this functionality. While we have restricted things from being externally access and yes of course they can download and send these files anyways it does create a bit of a loophole in our security plan.

Is it possible to limit the share functionality or at a minimum restrict access to be for those with existing access?

[#2]

Here is the article for the sharing features. Keep in mind the SharePoint one trumps the oneDrive setting, so if you don't want to affect onedrive you will have to do it individually across the board using the New SharePoint UI, but preferably, you would have to script it so that all your sites get updated on a routine basis so new sites cannot share.
https://docs.microsoft.com/en-us/onedrive/manage-sharing

The Powershell is Set-SPOSite -Identity $siteCollectionURL -SharingCapability ExternalUserSharingOnly but you would have to get creative with getting all your objects using get-sposite and filter based on URL search etc. so you don't overwrite sites you don't want to change.