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If your Confluence site is open to the public (you allow anonymous users to add comments, create pages etc) you may find that automated spam is being added, in the form of comments or new pages.
You can configure Confluence to deter automated spam by asking users to prove that they are human before they are allowed to:
Related pages:
Captcha is a test that can distinguish a human being from an automated agent such as a web spider or robot. When Captcha is switched on, users will see a distorted picture of a word, and must enter it in a text field before they can proceed.
Screenshot: Example of a Captcha test
By default, Captcha is disabled. When enabled, the default is that only anonymous users will have to perform the Captcha test when creating comments or editing pages. You can also choose to enforce Captcha for all users or members of particular groups.
You need System Administrator permissions to configure Captcha for spam prevention in Confluence.
To enable Captcha for spam prevention in Confluence: