Security of data
The security of data means the protection of data. The term refers
to all methods of protecting data and software from being:
Data is said to corrupt if errors are introduced into it. Usually the errors
have been introduced by faulty equipment.
disclosed to someone who should not have access to it.
Danger to files
Files may be in danger of accidently or intentionally being :
1. lost, e.g.
2. destroyed, e.g.
by losing discs;
because the file is on the system but badly named
3. corrupted, e.g.
by fire or flood;
4. modified, e.g.
by scratches on a disc or faulty disc drives;
by interference during a communication.
5. accessed by unauthorised people.
by being unintentionally written over;
by being updated with incorrect data.
Hacking means obtaining access to a computer system without authority.
Many examples of hackers are
programmers within the company concerned ;
someone from outside that use a modem from their own home computer to connect
to the computer being hacked.
someone that gained access to the electronic mailboxes of famous people.
A computer virus is a program which copies itself without the user intending
it to. Often a virus attaches itself to other programs which are then saved
with the virus added to them. Most viruses do not affect data files. The
virus usually does more than just copy itself. It may erase files or corrupt
the data on the screen.
Viruses cost commercial firms a great deal of money. Even if their computer
are not infected, they have to spend money making sure viruses are not
introduced. Step they can take are:
make sure everyone in the organisation knows of the danger.
use a commercial program which detects any viruses. Many of these can say
which viruses are present and get rid of them.
avoid the used of any programs of doubtful origin, such as 'free' software.
back up files on a regular basis. This may not get rid of the viruses,
but if it deletes files, at least they can be recovered.
make standard software write protected, so that a virus cannot change it.
Making copies of files
Data can be protected from destruction or modification by keeping copies,
although care has to be taken that this does not make unauthorised access
easier. A backup file is a copy of a file which is kept in
case anything happens to the original file. An achive is
a file or set of files which is being kept in long term storage in case
it is required.A backup files may be created by the user or may be produced
automatically by the system.
A particular word processor has two automatic backup facilities.
Backup files and archives use a large amount of storage. Methods are devised
of storing the data in a smaller space. A compression program is run which
changes the individual bit p;atterns of the characters as they are being
stored so that the data takes up less storage space. The disadvantage of
this system is that it takes time to decompress the data again if it is
to be used.
Backup on saving. This is to ensure that when the user saves
file the old version is not lost. The old version of the file automatically
renamed before saving the new one. The old one is given a name ending in
BAK so that the user can easily recognise what it is, e.g. LETTER.BAK is
the old version of LETTER.DOC.
Timed backup. This option is useful if there is a power failure.
The word processor automatically saves the documents in use every 15 minutes.
Other ways of looking after data
1. Locking files away.
2. Protecting files against being overwritten
To protect against fire, flood or theft, backup files and software are
often kept in another building in a fireproof and waterproof safe.
Important data stored on floopy discs should be kept in a safe place.
3. Keeping people out
Large magnetic tapes usually have to be fitted with a write permit ring
before data can be written on them.
Tape cartridges have a small tab on the edge which can be sbapped off to
prevent anyone writting data on the tape.
Tha data on floopy discs can be protected by sliding a small write protect
Only authorised personnel are allowed into certain area of many computer
A large computer system or a netword may have many users and many terminals
or workstations. Use has to be restricted.
A user identify (ID) ia a name or number by which the
system knows that the user. Each user is given an area of backing store
in which to store files. Often the user can decide which other users can
access these files.
A password is a set of characters which a computer associates
with a particular user identify. The password is known only to the user
an usually he or she selects it. A password is usually kept secret and
the computer does not display it on the screen as it is typed in.
Users of the system with user identities dan passwords have to log
in and log out every time they use it. To log in
means to gain access to a system by giving the correct instructions and
responses. To log out means to exit from a system by giving
the correct instructions.
Example of a log in and log out sequence.
Logging in. When you first come to a station a menu asks
you which file server you require. You select one using the mouse. A screen
appears with spaces for user identify and password. You type these ini.
The user identify appears as you type it but the password does not. A main
menu then appears for you to select the software you wish to use.
Logging out. When you have finished using s software packages
you exit from it. You then return to the main menu. This has an option
"Exit from the network" which you can select to log out.
Advice about passwords.
Many hacking problems arise from people finding out passwords or guessing
them. Your files are much more secure if you stick to the following rules.
Choose a sequence containing no fewer than six characters.
Pick something you can remember but no-one else would think of, even if
they know you.
Never tell anyone what it is.
Never write it down.
Be careful who is looking over your shoulder.
Change it every week or so.
Other software safeguard
Some files may only be accessible to certain password.
On some systems users may be able to give files an access code. For example,
a file may be made "read only".
Individual files may be given passwords.
Data encryption. The encrypt data is to encode it in such a way that is
unreadable to anyone who does not know how to decode it.
[ Kembali ke depan ]