To provide a system account (ex. DOMAIN\Username) access to SharePoint site crawling, it’s pretty easy to accomplish.
- Open Central Administrator
- Under Application Management, click Manage Web Applications
- Highlight the application that you want to add rights for and click the User Policy button in the ribbon bar.
- In the Policy for Web Application window, click on Add Users
- Leave default of All Zones selected and click the Next button
- Add the user account to add rights for, select the rights level and click the Finish button