Hi Thang Mo,
Thanks for your post.
The lock icon means that the folder or file has limited user access. And if there is no issue for user access, then we can safely ignore this lock icon.
In order to remove this icon, you can try to add the Authenticated User group
under the Security tab. Hope it helps.
For more information, you may refer to the following thread discussed the same issue.
How do I get a lock icon on my folder to come off?
http://social.technet.microsoft.com/Forums/fi-FI/w7itprosecurity/thread/e8347f6f-e835-42e1-8509-eee38f83bb05Best Regards,
AidenAiden Cao
TechNet Community Support
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