Computer Virus

In this blog we will learn about
  • computer virus 
  • Harmful effect of computer virus
  • Symptoms of compute virus
  • Different types of computer virus
  • Ways of Spreading virus 
  • Protection against virus
You must have heard about software. Computer virus is also a software. Computer virus is a destructive program. It destroys data, information and other programs on computer. Due to computer virus computer doesn't function normally. Like corona virus hide and act as parasite on human begins, Computer virus also hide themselves in other host files. So you cannot see computer viruses on a computer. same like corona virus computer virus can replicate and transfer from one computer to another computer without the notice a user. You don't need to transfer or copy computer viruses. When you transfer files, computer virus automatically transfer from one computer to another. All computer viruses automatically transfer from one computer to another. All computer virus can hide, replicate and spread. A computer virus may corrupt or delete data on computer. It may even delete every thing on hard disk. A virus is  inactive until you have executed an infected program or application or you have open the infected disk/drive. once virus is active, it loads onto the computer's memory and is saved.
Computer virus is the destructive program able to replicate itself in hard drive or system files by making copies of it and disturbs normal functioning of computer.

Many virus are not very harmful as they only display a message or produce sound when active. Other viruses make your computer system behave irregularly or to crash frequently. Therefore if the computer is not operating properly it is good practice to check for virus with the help of different utility software like windows defender, antivirus etc.

In simple language computer virus is harmful software or programs that disturbs the normal functioning of computer

Some of the common viruses are listed below:
  • C- Brain virus
  • logic Bomb virus
  • I love you virus
  • Disk killer virus
  • Time Bomb virus etc
Symptoms of computer virus: 
The following symptoms may indicate that your system have been infected by viruses:
  1. Computer runs slower than usual
  2. Programs takes longer time to load
  3. Disks or disk drives are inaccessible
  4. Program files and folders are hidden from the computer
  5. Renaming the files with different names
  6. Program runs automatically without any instructions
  7. virus changes the size of the file 
  8. Frequently display error message or image on the screen
  9. Fail to load operating system or other programs
  10. corrupting the system file
You can make computer system free from viruses or remove viruses using antivirus software. Antivirus software is type of program designed to detect and remove viruses from computer system. Antivirus software is a program that prevents and cleanups computer viruses from your computer system. It is also used to scan downloaded files as well as your entire computer system in order to detect the virus infection. Having a good and antivirus program and current updates is one of the best way to protect your system against virus attacks.
There are many antivirus programs some of them are listed below:
  1. Norton antivirus
  2. McAfree Antivirus
  3. AVG antivirus
  4. kaspersky Antivirus
  5. Avast Antivirus
  6. NOD 32 Antivirus
  7. Avira Antivirus etc.
Spreading of computer Virus
Computer virus spread from on computer to other computer through different external sources like infected hard disk CD/ DVD, pen drive etc. computer virus can also transfer on network or internet. some of the ways through which virus spread from one computer to other computer are as follows:
  1. using infected storage device
  2. by downloading files or programs from unsecured websites
  3. use of infected data or program in hard disk
  4. use of pirated software
  5. Exchanging of infected data or files over network
  6. Opening virus infected email messages or attached files without scanning   
Protecting computer from virus 
As virus are harmful program that affect computer .Virus can damage or corrupt our important file and slow down your system. Therefore protection and prevention of virus is very important. To protect computer from virus follow the following points
  1. Always load software from original disk or CDs
  2. Install antivirus program
  3. do not open email from unknown source
  4. do not use pirated software
  5. turn on firewall
Types of computer virus
Computer virus are classified depending upon the  infection method their origin, techniques, types of file they infect , the kind of damage they cause, the type of operating system attack. Some of the common types of computer viruses are discussed below:
Boot Sector Virus:
  • boot sector us area of computer which is accessed  when computer is turn on
  • boot sector virus infects Master boot Record(MBR) of disk and allows virus to spread fast and cause damage
  • it modifies the MBR that contain a boot record  program which is required loading OS
  • virus is loaded onto memory when computer is turned on when this virus is there in computer
  • boot sector virus is transferred from infected disk or drives
  • e.g. Disk Killer, Polyboot.B, Disk Killer, Danish Boot , Stoned etc
File Infector Virus
  • infects file that contain executable codes or file having extension .exe, .bin, .sys or .drv and many more file
  • aka program virus and can cause permanent damage to file
  • stays in memory and infect
  • many completely overwrite the file or may only replace parts of file that infects
  • only way to disinfect file from this virus is to ensure that the file affected with the virus have to be detected  and restore or baking up file is also the better option
  • e.g. Acid Rain, Die hert, Crazy.A, Cascade Dark Avenger etc
Multipartite Virus
  • behave like many other viruses and some times more than one type so its aka hybrid virus
  • infects boot sector and program file on disk
  • has combination features of both boot sector and file infector viruses
  • spread in many ways and is difficult to repair
  • if boot area has been cleaned but not the program file it will still infect 
  • e.g. Flip, One_Half, Emperor, Invader, Tequila etc
Stealth Virus
  • is hidden computer virus that attacks operating system processes and prevents typical antivirus or anti malware scans
  • uses various mechanism to avoid detection by antivirus software or has ability to hide itself
  • hides in files, partition, boot sectors and self copy to undetectable computer areas
  • this virus is difficult to detect and delete for few antivirus programs
  • e.g. Brain, Frodo, Joshi and whale are example of stealth viruses
Polymorphic Virus
  • computer virus that changes its code whenever it passes to another computer and change its appearance with every infection
  • it create infection in computer known as polymorphic infection that create copies of itself 
  • this could have 100s & 1000s of alternatives
  • even the best antivirus program can have trouble with detecting and cleaning polymorphic  infection
  • this virus is more difficult to find and remove
  • first polymorphic virus wass '1260' written by Mark Washburn in 1990
  • e.g. MtE, Satan Bug, Evil, Phoenix, Elkern, W95/HPS and W95/Marburg etc
Macro Virus
  • Macro is set of command used by program to perform common action
  • macro virus is a computer virus that infects macro file and whenever any macro is executed it shows its effects by altering or replacing macro code
  • this virus tends to be surprising but relatively harmless
  • once this virus is entered into computer it embed itself in all future documents
  • Antivirus program can protect your computer system against macro virus
  • W97M.Melissa, W97M.Marker, Word.Marco.DMV, Word.Macro.Hot, Word.Macro.Concept and Wordd.Macro.Nuclear are example of macro viruses.  
Script Virus
  • Script is very much similar to macro
  • Scripting virus is written in language understood by service run by operating system
  • Script virus is a type of computer virus that infect program prepared  in scripting languages such as Visual Basic and JavaScript
  • infect a computer through different scripting environment like windows help, windows registry files and windows installation files
  • can be spread by attaching themselves to data file, emails, and portable disk
  • First virus, Love stages JS. Fortnight and I Love You are example of script viruses 
Worms
  • Computer worms are destructive computer program designed to spread through computer network
  • these types of programs replicate from a computer to another computer by spreading entire copies of itself instead of infecting files or operating system
  • It can be transferred through emails or message contains executable codes
  • when computer is infected with worms they block network connection and make network traffic slow
  • worms can easily penetrate using most firewalls and other network security measures
  • sasser, earthworms, Blaster, Code Red, Dabber and fresh water leeches are some example of worms
Torjan Horse
  • Torjan horse is a harmful program that does not reproduce by  infecting other files nor do itself replicate like worm
  • It seems to be something desirable and contains malicious code
  • code when triggered cause loss or even theft of data
  • name came from greek mythology on the Trojen war
  • Trojen hose is one of the most common method a criminal uses to infect you computer and collect personal information from you computer
  • Vundo, ZeroAccess, Koobface,Flashback Trojan and Back Orifice are example of Troje horse programs
Logic Bomb
  • Logic bomb is a piece of code inserted into operating system or software application that implements a malicious function after some time or when specific condition are met.
  • Logic Bomb are often used with viruses, worms and Trojan horses 
  • It is destructive program which lies inactive until a specific piece of program logic is activated
  • different from virus as it does not replicate
  • It performs action like corrupting or altering data, reformatting a hard drive and deleting importing files
  • aka slag code or malicious logic
  • The jerusalem virus is type of logic bomb virus which deletes all the files on an infected computer every 13th Friday

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