Files used in applications are vital to the running of a system. Any loss or corruption of data will have serious or fatal implications for the performance of the application. Delays, loss of business and possible legal action may result. For these reasons many safeguards are used to protect files from:

• Hardware failures - all hardware dies eventually.
• Software failures - programming bugs can be hidden for a long time before a rare combination of events reveals the problem.
• Human Errors  - Accidental changing of data or deletion of files.
• Deliberate damage - may be caused by an angry employee, a virus or a hacker.

Physical Security

• Security guards
• Alarm systems
• Locks on rooms and on computers
• Access to rooms by swipe cards / fingerprint scan / retina scan
• Write-protect mechanisms - some drives and memory sticks have write-protect tabs. When switched on, the changing of data is impossible.

Passwords - Levels of permitted access

In order to gain access to the system a user is supplied with a user name together with a personal password. The operating system will check the user name and password are valid before allowing the user to log in.

Some files may be open by anyone, others only by those users with a particular level of access. It is possible that some levels of access allow a user to read but not change the data. The main computer's operating system makes sure that file access is appropriate for the user's password.

File Attributes

The file itself has attributes that can be set. The commonly used ones in Windows are:

• Read-only - the file can be read but not altered
• Hidden - the file is not displayed in listings of files.

Firewalls

Computers connected to networks - especially the Internet - need to be protected from hackers. Firewalls are software methods of blocking access to anyone from outside a network unless they are authorised.

Encryption

To maintain file security when data is transferred from one computer to another the data can be encrypted.

This means that the data is encoded in some way before it is sent, and therefore meaningless to anyone intercepting the message. The data is then decoded at the receiving end by the user who knows the way to decrypt it (often referred to as the key).

Data encryption can also be used when data is stored on a file. A hacker accessing the data will find it meaningless unless he has the key.