Some programs need narrowly controlled access that their callers do not ordinarily have. On an executable regular file, the set-user-ID bit can cause a new process to receive the file owner's user ID as its effective user ID. The program can then perform operations authorized for that identity while retaining information about the caller.
Permissions · Lesson 5
Setuid
Learn how the set-user-ID mode bit affects executable programs and why it requires careful security review.