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  • Viruses, worms and Trojan Horses are all malicious programs that can cause damage to your computer,

  • but there are differences among the three.

  • What Is a Virus? A computer virus attaches itself to a program

  • or file enabling it to spread from one computer to another, leaving infections as it travels.

  • Like a human virus, a computer virus can range in severity: some may cause only mildly annoying

  • effects while others can damage your hardware, software or files. Almost all viruses are

  • attached to an executable file, which means the virus may exist on your computer but it

  • actually cannot infect your computer unless you run or open the malicious program.

  • It is important to note that a virus cannot be spread without a human action, (such as

  • running an infected program)

  • What is a worm? A worm is similar to a virus by design and

  • is considered to be a sub-class of a virus. Worms spread from computer to computer, but

  • unlike a virus, it has the capability to travel without any human action.

  • The biggest danger with a worm is its capability to replicate itself on your system, so rather

  • than your computer sending out a single worm, it could send out hundreds or thousands of

  • copies of itself, creating a huge devastating effect. One example would be for a worm to

  • send a copy of itself to everyone listed in your e-mail address book. Then, the worm replicates

  • and sends itself out to everyone listed in each of the receiver's address book, and the

  • manifest continues on down the line.

  • Due to the copying nature of a worm and its capability to travel across networks the end

  • result in most cases is that the worm consumes too much system memory (or network bandwidth),

  • causing Web servers, network servers and individual computers to stop responding.

  • What is a trojan horse? The Trojan Horse, at first glance will appear

  • to be useful software but will actually do damage once installed or run on your computer.

  • Those on the receiving end of a Trojan Horse are usually tricked into opening them because

  • they appear to be receiving legitimate software or files from a legitimate source.

  • Some Trojans are designed to be more annoying (like changing your desktop, adding silly

  • active desktop icons) or they can cause serious damage by deleting files and destroying information

  • on your system.

  • Trojans are also known to create a backdoor on your computer that gives malicious users

  • access to your system, possibly allowing confidential or personal information to be compromised.

  • Unlike viruses and worms, Trojans do not reproduce by infecting other files nor do they self-replicate.

Viruses, worms and Trojan Horses are all malicious programs that can cause damage to your computer,

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