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protect your computer or a network of computers of an organisation from unauthorised access of data.

                    • Encrypt Data: Data encryption is converting the readable data into unreadable encoded form to save it from
                   unauthorised access. Sometimes sensitive data like personal credit card transactions you do in online purchasing
                   or data from defence services need to be transmitted through the internet or any other network should be
                   encoded to protect the information.

                    • Secure Sites: Websites that you access should be secured websites to avoid data hacking specially when you
                   do online transactions using your bank details or credit cards. If the site address starts with https:// and a lock
                   symbol, then it is safe to access.


                         Protecting Computer Against Viruses


                 VIRUS is an acronym for Vital Information Resource Under Seize.
                 Computer virus is a malicious code that attaches itself to a file and enters your computer system and makes copies
                 of itself and carries out the harmful tasks in such a way that it damages the important files of an operating system
                 or application programs or important data files  due to which the computer may stop working.
                 There are various types of virus. Some of them are:
                 •  Program File Virus: A program file virus, also known as file-infecting virus is a type of computer virus that infects
                   executable files (program files such as .exe, .com, .sys, etc. files) to make them unusable or damage permanently.
                 •  Boot Sector Virus: Boot sector virus is one of the most hostile types of computer viruses that infects the boot
                   sector or the Master Boot Record (MBR) of hard disks or floppy disks.

                 •  Macro Virus: A macro virus is a type of computer virus that is primarily designed to infect a specific type of
                   documents such as Word or Excel files.

                 •  E-mail Virus: E-mail virus is a type of computer virus that transmit from one computer to other through e-mail
                   messages.
                 Some of the viruses are designed to get activated at a certain date and time. No matter how advanced an anti-virus
                 software program you have installed in your computer the new malicious code will still find its way through your
                 computer defence system. They gain access to your computer through:

                 Infected files
                 •  Infected pen drives, CD/DVD-ROMs
                   • Through infected file attachment of emails
                 •  Insecure websites                              • Online
                   games
                 You will come to know  about  the virus that  infected your
                 computer through the following common symptoms:
                 •  Computer runs very slow as it loses its processing speed.
                 •  There will be a change in the system file size.

                 •  An unusual increase in number of files.
                 •  Computer restarts on its own in between.
                 •  Disk drives or disks become inaccessible.
                 •  An application or applications are not working correctly.
                 •  The computer locks up frequently or stops responding.

                 •  Dialogue boxes and menus sometimes appear to be distorted.
                                                               Information & Communication Technology Skills-II  63
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