User can change his Default Search Type and Default Search Mode as per his uses and requirement from My Preference settings.
To access My Preferences from eB Web, user should must have "User Information / User Preferences" permissions.
Step to Accomplish :
1) Make sure that user have required permissions to access "My Preference" settings from eB Web.
2) In eB Web, select eB icon which is for "My Preference and application information"
3) Extend eB Web node and there we can find "Default Search Mode" and " Default Search Type", from here user can set setting as per requirement.