Computer viruses


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Computer viruses

  1. 1. Computer viruses• Created by:-• Jagath• Pankaj• Pratish• Rasika• Niraj
  2. 2. What is a computer virus?• A computer virus is a computerprogram that can copy itself and infect acomputer without permission orknowledge of the user.• A computer virus can only spread fromone computer to another when its host istaken to the uninfected computer, forinstance by a user sending it over anetwork or the Internet, or by carrying iton a removable medium such as a floppydisk, CD, or USB drive.
  3. 3. History of computer viruses• 1981 Apple Viruses 1, 2, & 3• 1980’s Fred Cohen• 1987 Lehigh Virus• 1988 The first anti virus software• 1990 The first polymorphic viruses• 1991 Symantec releases Norton AntiVirus• 1992 The Michelangelo Virus• 1994 Kaos4 virus spreads via adultwebsites.
  4. 4. Virus through the internet• Today almost 87% of all virusesare spread through the internet.• Transmission time to a new hostis relatively low, on the orderof hours to days• “Latent virus”
  5. 5. Symptoms of virus Attack• Computer no longer boots up.• Screen sometimes flicker.• Computer runs slower then usual.• PC speaker beeps periodically.• System crashes for no reason.• Files/directories sometimesdisappear.• Denial of service (dos)….. & ManyMore.
  6. 6. Examples of risky file types• The following file types should be treated withsuspicion and be confirmed with the sender beforebeing opened:– .exe– .pif– .bat– .vbs– .com
  7. 7. What to do when you find viruses Firstly, you should call the administrator forfuture action. In some cases it is not good tostart you computer from hard disk, becausethe virus may active and then do some harm. Make sure that you should get sure that it isvirus and what virus it is. It is important toknow what kind of virus we are dealing with.Companies that make anti-virus programsknow what different viruses do and you cango to their web pages and read about thevirus you have.
  8. 8. Cont…… When you start you computer you should doit from a clean (non-infected) floppy disketteand after that run the virus program. Theboot diskette should be write protected sothat virus can not infect the boot diskette too. It is good to take a backup of the file that wasinfected. Virus program could do somedamage to the file and that is why it is goodto have a backup. It is good to let you, to know about the virus,so viruses would not spread around so much.
  9. 9. How to protect from virusesBest way to protect yourself is to prepare your computeragainst viruses in advance. One way to protect youcomputer is to use updated anti-virus program. When youget an email attachment, you should first check theattachment by checking the file with an anti-virus program.One can protect the computer against boot sector virusesby setting the BIOS to start from a hard disk rather thanfrom a floppy disk.Write protection is a good way to prohibit against viruses.Write protection works well in floppy disks, Windows NTand UNIX, but not that well in Windows and Windows95.
  10. 10. What is a computer WORM ?• A computer worm is a self-replicatingcomputer program. It uses a network to sendcopies of itself to other nodes (computerterminals on the network) and it may do sowithout any user intervention.• Unlike a virus, it does not need to attach itselfto an existing program. Worms almost alwayscause harm to the network, if only byconsuming bandwidth, whereas virusesalmost always corrupt or modify files on atargeted computer.
  11. 11. What are Trojan Horses ?• A Trojan horse, also known as a trojan, is malwarethat appears to perform a desirable function but infact performs undisclosed malicious functions.Therefore, a computer worm or virus may be a Trojanhorse. The term is derived from the classical story ofthe Trojan Horse.• A program named "waterfalls.scr" serves as a simpleexample of a trojan horse. The author claims it is afree waterfall screen saver. When run, it insteadunloads hidden programs, commands, scripts, or anynumber of commands without the users knowledgeor consent.
  12. 12. Types of viruses• Boot viruses• Program viruses• Multipartite viruses• Stealth viruses• Polymorphic viruses
  13. 13. How viruses get intocomputers• The four most common virus infections come from:– File – A virus type that infects existing files on the computer(approx. 40% of all viruses)– Macro – A virus that runs as a macro in a host applicationsuch as the MS Office applications (approx. 35%)– VBScript – A virus that uses Windows VisualBasic Scriptfunctionality (approx. 10%)– Internet Worm – A virus that is primarily characterized byit’s replication across the Internet (approx. 5%)
  14. 14. Basic virus defense• Be cautious of files that you are not expecting and fromunknown senders.• Many viruses automatically send files without the email accountowner’s knowledge. They can ‘piggyback’ on the email accountsof senders you know.• Be suspicious of messages that appear more than once in yourInbox• Be aware of sites offering free software downloads
  15. 15. Basic virus defense (cont.)• Learn file extensions– Your computer will display both an icon and a fileextension for every file.– Open only file extensions you know are safe.
  16. 16. ANTIVIRUS• Antivirus software are computer programs thatattempt to identify, neutralize or eliminate malicioussoftware. The term "antivirus" is used because theearliest examples were designed exclusively tocombat computer viruses; however most modernantivirus software is now designed to combat a widerange of threats, including worms, phishing attacks,Trojans, often described collectively as malware.
  17. 17. 2009 AntiVirus Software ProductComparisons
  18. 18. Removal Of Some Common Viruses• You can remove some of the commonviruses without help of any antivirusProgram.• Eg : New Folder.exe• Autorun.inf ( from PDs etc)
  19. 19. New Folder.exe• It looks just like an folder but actually it is a exe file.• Step 1: Try deleting the file.• It will delete if you haven’t executed it, if you’re unable to delete it• Go to Task manager ( by pressing ctrl+shift+esc )
  20. 20. Go to Process Tab andtry finding that theprocess for the exe fileand end the process.Then Go to the samefolder containing theexe file and delete it.Then Open Search andtry finding the .exe filesof same size and deletethem all.
  21. 21. Removal of Autorun.inf• Open Run dialog Box. Type in “CMD”press ENTER.
  22. 22. Cont…….• The Command Prompt will Open Now. In Command prompt go to the drivecontaining Autorun.inf• Now Type In “ attrib –h –s –a” and press enter.• This will remove drives attributes for all Hidden, System files.• Now Type “ Delete autorun.inf” and press Enter.• The Virus has been Successfully Removed.
  23. 23.  Data Fellows F-Prot EliaShim ViruSafe ESaSS ThunderBYTE IBM Antivirus McAfee Scan Microsoft Anti-Virus Symantec Norton Antivirus S&S Dr S&S Dr Solomons AVTK. Bit Defender 2008
  24. 24. * How computer viruses have spreadout around the world * Computer viruses are a problem all over the world. Thefollowing picture tells us how many times people haveaccessed Data Fellows, a company that makes anti-virusprogram F-Prot, more than 1,672,846 per month. It means thatpeople are interesting in virus information. One reason is thatpeople have to deal with viruses. Viruses in not only a problemin Finland and USA, it is a problem around the world. Todays most common virus is the macro virus. Cap virus isone of the macro viruses. Last month there were 3100 Capmacro virus accesses during the last 30 days in Data Fellows.Next common virus was “Join” with 1171 accesses and thirdcommon was Pen pal Greetings with 895 accesses.
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  27. 27. conclusion There are lots of viruses in the world and new virusesare coming up every day. There are new anti-virusprograms and techniques developed too. It is good tobe aware of viruses and other malware and it ischeaper to protect you environment from them ratherthen being sorry. There might be a virus in yourcomputer if it starts acting differently. There is noreason to panic if the computer virus is found. It is good to be a little suspicious of malware whenyou surf in the Internet and download files. Some filesthat look interesting might hide a malware.
  29. 29. Keep your pcsafe......./
  30. 30. THANK YOU