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    What is malicious code and can I download it accidentally using Skype?

    Malicious code is a computer program put on your computer either without your knowledge (such as when you browse an infected website) or which you are tricked into installing.

    Such code is called “malicious” because its creators want to use it to annoy, scam, or harm you or others, either through:

    • Damaging your computer’s inner systems, such as wiping its data or interfering with effectiveness.
    • Using your computer to relay spam emails and viruses to your friends and contacts over the internet without your knowledge (a network of such infected computers is called a “botnet”).
    • Spying on your activities to steal personal information to be used in identity theft (such programs are called “spyware”. 

    What does malicious code look like?

    Malicious code can take many forms, such as:

    Type Description

    These attempt to run on your computer when you visit an infected website. Most modern browsers will give you a warning that a website wants to run a script when it happens. There are in fact many legitimate reasons a website may try to run a script on your computer – for instance, some websites will try to put a little file on your computer that remembers your details for your next visit (such a file is called a “cookie”) so you do not have to enter them again, so it can be hard to tell when a script is malicious. 



    These are a kind of virus, sent through emails and increasingly also through instant messaging. They are often hidden in an instant message or email in the form of an attachment, and the email will try to persuade you to open it. Some worms can mimic the email address of a friend in your contact list, to make you more likely to open it.



    These programs are spread through network links between computers. They work by installing themselves on the infected computer and giving it instructions, usually to interfere with the computer’s effectiveness or damage it, and also to distribute itself to as many other computers as possible.


    Trojan horses These malicious downloads include code hidden in other programs which the user actually wants to download. For instance:
    • Music or movies downloaded illegally from the internet can frequently host malicious code.
    • A user may encounter a pop-up message warning the user that their computer has failed a security check and needs to upgrade.
    • A company the user trusts may seem to contact them with instructions to download a “patch” or upgrade, such as a chat message from someone purporting to work for Skype.

    This way the user will be tricked into downloading the program. Once installed, it is under the control of another person and your computer is then vulnerable to them if you have insufficient security.

     How can I avoid downloading malicious code?

    The best way to avoid malicious code of all kinds when using Skype is to ALWAYS have up-to-date security software. There are many different kinds on the market, some of them free.

    They can include the following features:

    Anti-virus software – this checks your computer for signs of viral activity and scans it against a database run by the anti-virus company. If a match is found, the program discovered will be disabled or deleted.

    Browsing security – this scans websites you browse to and checks whether they are legitimate. If not, you will be advised of any problems. Additionally, scripts such as cookies cannot be run or downloaded without your express permission.

    Firewall – this feature protects your computer from intrusion from the network. Only trusted connections will be made between your computer and the network.

    To learn more about your online security, safety and privacy, visit our security center.

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