Monitor the content of your network websites with WPMU Content Monitor plugin. You can filter the bad words that are available or posted in your multisite. You can set any number of emails that will receive the warning email in case of any bad word is found. An instant notification will be sent to the admin in case of any matched criteria.You can easily enable to disable the filter.
This is the EXACT same plugin as distributed by the developer on WPMU DEV. The developers’ links are provided above.