[0] Search Service Default Content Access Account(e.g. sp_search_content) [1] Crawl contents unless different authentication method is specified by a crawl rule for a URL or URL pattern [3] None [4] None [5] Account will be added to the Full Read policy *, giving it read-only access to all content web applications This account will be assigned to the db_owner role for the associated search service application databases (e.g. Search DB, Crawl DB, and Property DB) during search crawl [2] 
Must be a domain user account and it must have read access to external or secure content sources that you want to crawl by using this account. For SharePoint Server sites that are not part of the server farm and cross-farm scenarios, this account must be explicitly granted full read permissions to the Web applications that host the sites from the central administration. Must not be a member of the farm administrators group.