Why are you posting the same question 3 times in the same topic? This doesn't help you in getting a solution faster and it is frustrating for both you as the people helping you that you get information you already have through another question.

https://www.servicenow.com/community/developer-forum/1-restrict-attachment-for-others-groups/td-p/31...

https://www.servicenow.com/community/developer-forum/restrict-attachment-for-others-groups/td-p/3104...

https://www.servicenow.com/community/developer-forum/1-1-restrict-attachment-for-others-groups/td-p/...