You want to prevent other users on your machine from reading your files.
To protect existing files and directories:
$ chmod 600 file_name $ chmod 700 directory_name
To protect future files and directories:
$ umask 077
chmod and umask are the most basic file-protection commands available for Linux. Protected in this manner, the affected files and directories are accessible only to you and the superuser. (Not likely to be helpful against an intruder, however.)
The two chmod commands set the protection bits on a file and directory, respectively, to limit access to their owner. This protection is enforced by the filesystem. The umask command informs your shell that newly created files and directories should be accessible only to their owner.
chmod(1). See your shell documentation for umask: bash(1), tcsh(1), etc.