How to censor words in phpBB3
Word censoring in phpBB3 is actually enabled by default. What you need to do, however, is to make a list of the words that you want to be censored. To do this log in to the administration control panel, then click on the Posting tab and after that on the left side click on Word censoring.
If you haven't used word censoring so far, you'll see an empty table. Click on the Add new word button above the upper right corner of the table. You'll see two text fields, one labeled Word and the other Replacement. In the field for Word type the word that you want to be censored and in the field for Replacement type what you want to replace the censored word. In this way when someone types in a post a word that's in the censored words list, it will be replaced with the word (or symbol) you have specified in the Replacement field. Don't forget to click on the Submit button after you type both words.
You can also use wildcards (*) before or/and after the word to be censored. For example, if you type *ed in the text field for Word, all words that end with ed will be censored.
By default registered users cannot disable word censoring and only some of the predefined administrator roles (e.g. standard administrators) have permissions to alter word censors. From Post settings (Posting tab>Post settings), however, you can allow registered users to disable word censoring. Just mark the button Yes for Allow disabling of word censoring. In this way registered users will be able to disable it from their user control panel. From the Permissions tab of the administration control panel you can also allow only particular users or groups of users to disable word censoring, and you can give permission to other administrators, for example, to alter word censors.