The following tutorial gives a step by step guide to create a custom permission on a SharePoint site. This steps have to be followed on each site that needs to be crawled.
Any changes on the SharePoint site permission functionality may invalidate this tutorial. The following permissions were last checked on September 29th, 2021.
Go to Permission Levels page and click on Add a Permission Level
On the "Add a Permission Level" page, set a name and description for the new permission.
Set the following List Permissions:
Set the following Site Permissions:
Leave the Personal Permissions unchecked and click Create.
Assign the new permission to the crawl account.