WHAT IS A COMPUTER VIRUS?A computer virus is a small software program that spreads from one computer toanother computer and that interferes with computer operation. A computer virusmay corrupt or delete data on a computer, use an e-mail program to spread thevirus to other computers, or even delete everything on the hard disk..CHARACTERISTICS OF A COMPUTER VIRUS: the ability to replicate itself. the ability to attach itself to another computer file.
WORKING OF COMPUTER VIRUS A Computer Virus needs another program in order to be able tobe activated and infect other computers files. For example, a virus might attach itself to a spreadsheetprogram. Each time the program runs, the virus runs too. A file containing virus is called infested file.
TYPES OF COMPUTER VIRUSES Stealth viruses Use certain techniques to avoid detection. Macro Viruses Infects the macros within a document or template. Polymorphic viruses Encrypt its code in different ways Metamorphic viruses Rewrite themselves each time they infect a new file.
TYPES OF COMPUTER VIRUSES Boot viruses Affects boot sector of a floppy or hard disk. Program viruses Infect executable program files. Multipartite viruses A hybrid of Boot and Program viruses. Directory VirusDirectory viruses change the paths that indicate the location of a file
TROJAN HORSECovertLeaks informationUsually does not reproduce
WORMSSpread over network connectionWorms replicateFirst worm released on the Internet was calledMorris worm, it was released on Nov 2, 1988.
WHAT CAN VIRUSES DO? Format hard disk Copy, rename and delete files Modify files dates and extensions Display false message every few times Damage data Damage software
SYMPTOMS Computer runs slowly Random restarts Unknown and uninstalled icons on desktop Icons change in appearance System memory and disk space is reduced New windows open up at an alarming rate Error messages on regular basis Files mysteriously disappear
HOW VIRUS SPREADS? Email Opening and downloading an email containing virus Networks Connecting with network that contains virus Removable Storage Media Floppy discs, CDs and flash devices Pirated Software Installing pirated software that contains virus
W H O C R E A T E S V I RU S E S A N D W H Y ?Common people: For fun Release anger Take revenge For fameProfit earners: Antivirus marketInfo attackers: Disrupt enemy’s information and network
HOW TO PROTECT FROM VIRUS? Latest antivirus should be installed Antivirus software must be upgraded regularly Unknown emails should not be opened Unauthorized software should not be installed Removable storage media should be scanned Freeware and shareware software from internet should be checkedbefore installing
GENERAL SECURITY TIPS Apply user-level security on file sharing when needed. Dont open email attachments from unknown senders. Use Rich Text Format files instead of Word Documents. Updated anti-virus program Set the BIOS boot sequence Write protection