This is a very simple non - technical explanation of the problems commonly affecting computers.
A virus is a program written specifically to cause harm to a computer or a network.
A virus can also be designed to retrieve information from your computer to be delivered to an attacker for future use.
For example credit card information, passwords, and security access codes. Many different types of virus exist. Some examples are listed below:
A Trojan (or Trojan horse)
A malicious program that often pretends to be a benign application. It is designed to cause your computer to do something that is unexpected. Since it does not spread (it is not self-replicating) it is not strictly a virus.
A parasitic program designed to replicate itself on your computer and then spread to other computers via e-mail (through your address book) or an IRC (chat program). Some viruses are self-replicating and contain their own mechanism for spreading. The clever thing that some mass mailer viruses do, is to look at your address book, select the contents & send mail to each other, so your friends don't know that the virus is from you, as it is showing on the received email's address to be from someone in your personal address book who your other friends might not know.
How can my computer become infected?
The most common method of infection is via e-mail attachments. Your computer can become infected from running a program or opening a file from a floppy disk copied from an infected computer. It can become infected via files or programmes downloaded from the Internet or through IRC, AIM, ICQ or other instant message programs. However, some worms can spread without any intervention from a user. Such worms are usually exploiting a vulnerability on your PC. These worms can only be prevented by ensuring that your PC is secure.
Spyware or Parasites are programs that are installed to collect information about a user and report back to a remote site. These parasites are usually installed by freeware programs without the user knowing and can watch the activities of a user and send this information to a remote site. Activities may include keystrokes, passwords or just your web browsing activity, plague the user with advertisements, slow the system down or crash the user's system or generally make the user's system vulnerable to attack. To help prevent "Spyware" appearing on your PC, download "Spybot" & "Spywareblaster" from the web, then install the program, open it & click on "updates" run the check & then select "immunize". It is a good idea to clear your cookies & temporary internet files after every internet session. This is done by accessing "tools" - "internet options" & from there you can delete the cookies & temporary internet files. These temporary internet files are there to speed up access to web pages, they are unnecessary if you have a broadband connection, but useful if you only have a narrowband 56k modem connection.
How can I get rid of a virus?
Several Internet security companies provide tools specifically designed to scan your computer and remove known infections. McAfee provide a free scanning utility called Stinger, which can be downloaded from their website.
How can I protect my computer against future infections?
Some viruses are transmitted by other means than e-mail. You should therefore install and configure a good anti-virus program on your computer. Keep the virus definition files fully up to date. Anti-virus software programs can automatically check for new viruses and your anti-virus program should be set up to do this at least weekly. Your anti-virus program should be configured to scan e-mail, all files and folders, boot sectors and all removable disks (floppy and zip disks). If you receive an attachment or file via e-mail, or removable disk, that attachment should be scanned for viruses before opening it. It is also vitally important that you have applied the latest patches to the Operating System of your computer. If you have removed viruses but your Operating System remains vulnerable, your computer may well become re-infected.
What is a firewall?
A firewall is a device or application that is designed to keep hackers out and your personal data secure. Firewalls effectively create a barrier between your computer and the Internet and you decide exactly what type of traffic you want to allow in and out. Please bear in mind that security vulnerabilities are always being discovered. Though your PC may be secure today, the discovery of a new vulnerability tomorrow will mean you have to secure your PC once more. This is why anti-virus software is often updated and why companies like Microsoft are often issuing updates on their website. Even with a firewall installed & setup correctly, when browsing the internet, be careful not to accept automatic "downloads" from sites (grey dialogue box that appears & asks you to open a file if you wqant to access the site that you are looking at) To click "yes" would generally be very unwise, some of these dialogue boxes, if accepted, can install "webdiallers" which mean that when you next connect to the internet, instead of using your normal 0845 (local call rate) connection, the modem dials a number somewhere in Bankok, Thailand instead!