What is malware?
It is malicious software including, amongst other things, viruses, worms and Trojan horses.

What is a virus?
A virus is a program that normally attaches itself to another program or data file in order to spread and reproduce itself without the knowledge of the user. Normally a virus enters your computer through a spam email which has attachments (pictures or files). A virus can damage files or cause your computer to behave strangely.

What is a worm?
It is a virus that reproduces by replicating itself across a network of computer systems. A worm can harm a network, can consume tremendous bandwidth, and can shut a computer down.

What is a Trojan horse?
It is a program that appears to be working properly but actually causes damage in some form. It is called a Trojan because it can enter your computer through operations considered harmless, for example, through a game or even through a virus tracking program, and so it can trick the user by hiding the underlying activity. In general, Trojan horses cannot multiply themselves as viruses do.

What is a difference between a virus and a worm?
The main difference between a virus and a worm is that a virus cannot replicate itself like a worm, and it only affects the computer it has invaded. A worm acts autonomously, and uses a computer network in order to multiply itself and to send copies of itself to other systems.

How can I prevent malware from entering my PC?
It is important not to open any emails which come from senders you don’t know. Many of those emails have luring titles like “You have won a lottery” or “Happy birthday, I have a present for you” and so on. Never open any attachments coming with such emails, as it is likely that in such cases you will install a virus or a worm in your PC. As a rule, you should never open an attachment that has been sent to you by someone you don’t know.

Install an anti-virus software on your PC. This will protect your computer against viruses and other malware threats.

You can also install a firewall, which will keep watch on all files that go in and out of your computer. Try to avoid suspicious websites, and if you accidentally enter one which seems strange, leave it immediately. If pop-up windows alert you or ask you to agree to anything, immediately close them and never click on any button inside them.

What is an anti-virus software?
It is software that is used to protect a computer against viruses or other malware threats. The software is installed on your PC and checks against viruses all files on your computer as well as files attached in incoming emails. If it finds viruses, it immediately informs you and, in most cases, it quarantines/cleans the infected files.

An antivirus software needs to be regularly updated, and can also be used for security such as content- or website-filtering.

What is a firewall?
A device or software designed to prevent or stop unauthorised people from accessing your computer via the internet without permission. A firewall controls all the files that go in and out of your computer. If there is a suspicious file, it will take care of it for you and keep your computer safe.

What is spyware?
It is a program that can be secretly attached to files you download from the internet. As soon as it is downloaded it installs itself in your PC without your knowledge, and starts to monitor your internet activity. The monitored information is then transmitted to a third party, in most cases to companies which are interested in creating your personal profile. Later on, it will start sending you advertising or other data.

What is a hacker?
A hacker is a person who, without permission, gains illegal access to a computer system and its data, without the intention of causing any damage.

What is cracker?
A cracker is a person who, without permission, gains illegal access to a computer system and its data, with the intention of causing financial or other damage, and/or stealing information.

Which methods do crackers use?
Crackers normally insert viruses or other kinds of programs containing special code into target systems, with the intention of causing severe damage to the attacked system. In most cases, such code is:

• A Trojan horse, hidden in other programs or files, which seem to be harmless.
• A worm, which is not hidden in other files, but is sent through network security holes that have been spotted.
• A logical bomb, which is an idle code component within a bigger program, which activates itself on a certain date or event.

What is the difference between a hacker and a cracker?
Normally, hackers see their activity as a challenge and a pleasure in entering a highly secure computer system, and they don’t intend to cause any damage. Many times hackers enter a system (for example a banking or a government system) to reveal security holes. If they achieve their purpose, they inform the respective organisation about their success, hoping for financial benefits.

On the other hand, crackers try to illegally enter a computer system in order to steal data, or to cause damage to the information found in the system’s archives. For example, as soon as they get hold of a credit card number, they use it for their own benefit.

I have a dialup connection and used the internet for a couple of hours only but I got a huge bill at the end. Why? What can I do? - Dialers
This happened because, without your knowledge, a so-called dialer stopped your local internet connection with your ISP provider and redirected the connection to an international line with (in most cases) tremendous billing costs. This normally happens when a user visits an untrustworthy website with suspicious or erotic content.

If you have a dialup connection, you can contact your telecom company to ask what you can do to prevent a dialer from using your line. Its worth paying a little extra to receive a detailed phone bill that you should monitor regularly as dialers tend to parasite lines for as long as possible before they are detected. You could also ask your telecom company to limit your line to national calls. Although this may be very convenient, it would at least prevent a dialer from being able to re-direct your line to an ISP somewhere in the world.

Now go to your national node’s website to find useful links and further information.