What is the best approach for preventing users entering ftp sftp links and credentials in Jira

[Neeraj Mathur]

What is the best approach for preventing users from entering ftp sftp links and credentials in Jira Cloud. Can we restrict some keywords in Jira comment. 

[Nic Brough -Adaptavist-]

I cannot find anything that would prevent people from putting in any text they want into a free-format text field (description, environment, comments and so-on)

I think the best approach to this is not a technical one, but getting people to understand security better.  Why do your users think it's a good idea to share credentials?  If they are an employee, then what part of "gross misconduct can get you fired instantly" is not understood well enough?