When a process creates a new file, it specifies the permissions that it would like the new file to have. Often, the mode requested is 0666 (readable and writable by everyone), which is more permissive that we would like. Fortunately, Linux consults something called a "umask" whenever a new file is created. The system uses the umask value to reduce the originally-specified permissions to something more reasonable and secure. You can view your current umask setting by typing umask at the command line:

$ umask
0022

On Linux systems, the umask normally defaults to 0022, which allows others to read your new files (if they can get to them) but not modify them.