A computer virus is a computer program or file designed to deliberately cause other programs or data to malfunction. This malicious program can infiltrate your system and inflict extensive damage to the data and program on your hard disk.
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One can reduce the chance of downloading a virus from the Internet by following these words of advice.
don't open the email attachment from people you don't know. Any unknown email message from someone you've never heard before, and that message includes an attachment. The attached word file could contain a micro virus and the attached program could wipe out your entire hard disk. image source
always download programs from reliable sources. If you download files from the Internet, use only those established and reliable Web sites that actually check their files for viruses before they past them for downloading.
Always use anti-virus software : anti-virus programs protect you against all types of viruses and use the anti-virus program to check all new files downloaded to or copied to your system.
All system files should be backed up from time to time in addition to data file.
