All administrators (and non-administrators with the edit filter helper user right) have a user right which allows them to view hidden filters created through the Edit filter extension. Additionally, admins can assign themselves the 'Edit filter manager' user right which allows them to edit the contents and settings of edit filters. Great care should be taken if editing edit filters as even the smallest mistake can cause huge disruption.
See Wikipedia:Edit filter for the tool's guideline and MediaWiki:Extension:AbuseFilter/Rules format for technical help.