All files that are opened by a user or downloaded from a remote source, such
as the internet or a memory stick, are scanned to see if they match samples of
known virus programs that are stored in the anti-virus program's library
Any files that contain viruses are either blocked, deleted or have the virus
element of them removed
For this reason it is important to keep anti-virus software up to date so that its library
contains details of all known viruses
Any unusual activity on a computer is monitored by the anti-virus software
An example might be an attempt by a program to perform an unusual act such
as downloading a file from the internet
If the file matches anything the anti-virus software knows to be caused by a
virus it will prevent the action from taking place
Anti-spyware software works in a similar way
Details of spyware programs are stored in a
library and this is used to check all incoming
files to see if they contain spyware.
If they do, the file is blocked
Anti-spam software works by storing detaisl of known SPAM addresses - when an
incoming email message is sent from one of these addresses the message is diverted
into a spam folder where it will be deleted after a few days
Firewalls
A firewall is designed to prevent unauthorised access to a computer ot network from other
computers attached to it or connected over the internet. The basic way a firewall works is;
The firewall monitors all incoming and outgoing traffic to
and from the computer or network
Any incoming or outgoing data that has not been requested by the computer is blocked. For example, if John selects a web page, his
firewall will allow the request because it came from a user on his computer. However, if a user connected to that web page then tires to
gain access to John's computer, John's firewall will blobk the attempt as it wasn't requested by John or his computer
Encryption
Encryption is used to protect data whilst it is being transferred between two
computers over a network such as the internet. Data being transferred over the
internet can easily be intercepted by unauthorised computers.
One reason for this is that the system often uses telephone technology to transmit the data, and this can be
hacked into. Data encryption works in the following way;
Data to be transitted by computer A to computer B is first scrambled into a secret code by
computer A's encryption software, using an encryption key
The scrambled data is then transmitted over the internet to computer B
The same encryption principle can also be used to protect the data stored on a computer stores the data in
encrypted form and the user is required to enter a password before the computer decrypts the data for them to use.
In this way the data on portable and handheld devices such as laptops and PDA/smartphones can be protected -
unless a thief knows the encryption password they will be unable to use the data stored on the device.
Computer B recieves the scrambled data and then unscrambles it
using the same encryption key used by computer A
A very common use of data encryption is for making payments
for goods and services on the internet. The customer's personal
and payment information, such as address and credit card
number, are typed into a form held on a secure website. The data
is then encrypted before transmission over the website. The
address of secure websites always begin with the letters https://
and a padlock symbol is displayed in the status bar at the bottom
of the browswer window displaying the page