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Spam may include offensive material like profanity, pornography, or even viruses and other harmful software. Although
        it is possible to unsubscribe from spam, the process is time-consuming. A software tool for blocking spam is frequently
        offered by email providers, but it is not always efficient.

        8.3.9 Malware
        Malware is a program that aims to hurt a computer, server, client, or computer network. Attackers use malware to
        perform illegal actions on a user's computer, such as data collection, network or system damage, data encryption for
        ransom, and data erasure.  Computer viruses, worms, Trojan horses, ransomware, spyware, and adware are  examples
        of malware. Installing anti-malware software and keeping it updated is necessary to protect the system from malware.

        Viruses
        A virus is a piece of software code that can damage your system by replacing or messing up the system files. Computer
        viruses are like viruses that live in our bodies and copy themselves and damage cells. A typical virus attaches itself to
        a program and can spread to another piece of code or file that has not  been infected. So, the infection can spread
        from one computer to another. Unsuspecting users may exchange files on discs, USB sticks, or over a network  and
        contribute to the spread of viruses (Figure 9.2).




















                                                  Fig 15.7: Computer Virus
        Computer viruses make several copies of themselves. They add their code to system programmes, files, or the boot
        sector of hard drives, which makes them unusable. As a result, the system slows down or even stops functioning. The
        viruses are mainly classified as boot sector, file infector, and macro viruses.
        •  A boot sector virus is a virus that affects the boot sector of the disks. It gets activated when the drive is started
           (booted up). The Michelangelo virus is an example of a boot sector virus.



               A book sector is a part of secondary storage that contains instructions on how to boot (start) a device.



        •  File Infectors are viruses that attach themselves to executable files by overwriting a part of their code or appending
           their code to the files. For example, the Romeo and Juliet virus.

        •  Macro viruses embed themselves into the documents. A macro refers to specific instructions within an application.
           The macro viruses are executable files that may be  received as email attachments. When a recipient opens an
           attachment, the viruses gets activated and starts affecting the system programs (deleting, creating, or overwriting
           other files). For example, the Melissa Virus got  spread through a Microsoft Word document sent as an attachment.
           When the Word file was opened, the virus got activated. Using the Microsoft Outlook program, the attachment
           would be sent to the first 50 contacts in the address book.




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