What is the specific dangerous setting on a secret file (like one with passwords) that lets any user read it on a Linux system, making it a big mistake?

The specific dangerous setting on a secret file that allows any user to read it on a Linux system is when the 'read' permission is granted to the 'others' category. Linux file permissions control access to files and directories by defining what actions are permitted for different types of users. These permissions are assigned to three distinct categories: the 'user' (or owner) of the file, the 'group' that owns the file, and 'others.' The 'others' category, often referred to as 'world,' encompasses any user on the system who is neither the file's owner nor a member of its designated group. The 'read' permission specifically allows a user to view or copy the contents of a file. Therefore, if a secret file, such as one containing passwords, has its 'read' permission enabled for 'others,' it means that any user account on the Linux system can access and read its sensitive content. For instance, in common octal notation, a file permission like `644` (rw-r--r--) indicates that the file owner has read/write, the group has read, and critically, 'others' also have read access. In symbolic notation, this is visible as the last 'r' in a string like `rw-r--r--`. This configuration is a significant security mistake because it makes confidential information universally readable by all local system users, directly compromising data confidentiality and potentially leading to unauthorized access to other resources.