a computer virus is a computer program that can copy

8/14/2019 A Computer Virus is a Computer Program That Can Copy

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A computer virus is acomputer program that can copy itself and infect a computer. The

term "virus" is also commonly but erroneously used to refer to other types ofmalware,

adware, and spyware programs that do not have the reproductive ability. A true virus canonly spread from one computer to another (in some form of executable code) when its

host is taken to the target computer; for instance because a user sent it over a network or

the Internet, or carried it on a removable medium such as afloppy disk, CD,DVD, orUSB drive. Viruses can increase their chances of spreading to other computers by

infecting files on a network file systemor a file system that is accessed by another

computer.[1][2]

The term "computer virus" is sometimes used as a catch-all phrase to include all types ofmalware. Malware includes computer viruses, worms, trojans, most rootkits, spyware,

dishonest adware, crimeware, and other malicious and unwanted software, including true

viruses. Viruses are sometimes confused with computer wormsandTrojan horses, whichare technically different. A worm can exploit security vulnerabilities to spread itself to

other computers without needing to be transferred as part of a host, and a Trojan horse is

a program that appears harmless but has a hidden agenda. Worms and Trojans, likeviruses, may cause harm to either a computer system's hosted data, functionalperformance, or networking throughput, when they are executed. Some viruses and other

malware have symptoms noticeable to the computer user, but many are surreptitious.

Viruses can really only do one of two things, they can either delete files, or they can alter them. You're

probably asking yourself, "Then why are viruses so dangerous if all they can do is play with the files?" The

reason this is dangerous is because they can alter any file. Some viruses are designed to attack files in the

boot sector, this could make it impossible for your operating system to boot up, others attack system files

that are critical for your operating system to perform normally, still others are designed to specifically attack

your documents. If a virus infects a system file that is crucial to your system it is possible that that virus

would cause your memory to not be freed up causing what is called as a memory leak. If this occurs your

computer will gradually get slower as you use it, until eventually it locks up. These things may just seem like

minor inconveniences to you now, but if your computer is infected you will quickly find out how much trouble

it can really cause. There is of course the worst case scenario for viruses, the viruses might be designed to

completely erase everything on your hard drive, you may be thinking "No, problem I always back up to disk".

Well if you always backup than you put your disk in your infected computer, if it is a boot sector virus, guess

what, your backups are infected as well. Total data loss, no matter what you do. This is why it is important to

reduce your risk.

Your computer will get infected by a virus by opening the virus-file. This file will usuallybe: or: attached to an email-message or: under a button on a internet-site (sometimes even

by opening a site or perform some other action on the site). or: on a CD or other kind of

disc. or: a file, sent to you, through a messenger-servicComputer virus' come from the
http://en.wikipedia.org/wiki/Computer_programhttp://en.wikipedia.org/wiki/Computer_programhttp://en.wikipedia.org/wiki/Malwarehttp://en.wikipedia.org/wiki/Adwarehttp://en.wikipedia.org/wiki/Spywarehttp://en.wikipedia.org/wiki/Codehttp://en.wikipedia.org/wiki/Floppy_diskhttp://en.wikipedia.org/wiki/Floppy_diskhttp://en.wikipedia.org/wiki/Compact_Dischttp://en.wikipedia.org/wiki/DVDhttp://en.wikipedia.org/wiki/DVDhttp://en.wikipedia.org/wiki/USB_flash_drivehttp://en.wikipedia.org/wiki/Network_file_systemhttp://en.wikipedia.org/wiki/Network_file_systemhttp://en.wikipedia.org/wiki/Computer_virus#cite_note-0%23cite_note-0http://en.wikipedia.org/wiki/Computer_virus#cite_note-1%23cite_note-1http://en.wikipedia.org/wiki/Malwarehttp://en.wikipedia.org/wiki/Malwarehttp://en.wikipedia.org/wiki/Computer_wormhttp://en.wikipedia.org/wiki/Computer_wormhttp://en.wikipedia.org/wiki/Trojan_Horse_(Computing)http://en.wikipedia.org/wiki/Trojan_Horse_(Computing)http://en.wikipedia.org/wiki/Trojan_Horse_(Computing)http://en.wikipedia.org/wiki/Computer_programhttp://en.wikipedia.org/wiki/Malwarehttp://en.wikipedia.org/wiki/Adwarehttp://en.wikipedia.org/wiki/Spywarehttp://en.wikipedia.org/wiki/Codehttp://en.wikipedia.org/wiki/Floppy_diskhttp://en.wikipedia.org/wiki/Compact_Dischttp://en.wikipedia.org/wiki/DVDhttp://en.wikipedia.org/wiki/USB_flash_drivehttp://en.wikipedia.org/wiki/Network_file_systemhttp://en.wikipedia.org/wiki/Computer_virus#cite_note-0%23cite_note-0http://en.wikipedia.org/wiki/Computer_virus#cite_note-1%23cite_note-1http://en.wikipedia.org/wiki/Malwarehttp://en.wikipedia.org/wiki/Computer_wormhttp://en.wikipedia.org/wiki/Trojan_Horse_(Computing)


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internet, they are created by other computer users for a wide varity of reasons but mostly

for pure evilness

e.

1. An infected memory stick, diskette or other computer connected by a network caninfect the computer system

2. Downloading files that are already infected can infect your computer.

Modern Communication Woes

Like the telephone, email is one of the quickest and most convenient forms ofcommunication today. We send them through the office, to our children, and toour clients. We use it because it is quick and easy. We have electronic addressbooks instead of little black books.

Email frauds commit their crimes in a way similar to con artists who commit theircrimes over the telephone. How many times have you gotten a phone call from astrange source, asking you for money or personal information? When you askedthem to verify their company and you would call them back, did they back off?

Con artists over the phone seek to gain your trust. Creators of email virusesprey on you by claiming to be from somebody that they're not. The good news is,you really don't have to be a victim, if you're armed with the right information.

Arm Your Computer

Anti-Virus software is a necessity nowadays. If you don't have it, now is the besttime to shop for it! In lieu of the recent virus attacks, many of anti-viruscompanies are giving away free 30-day-trials. (Just remember the deal is muchsweeter when you're downloading it before your computer catches a virus!) Youcan shop around on the Internet for the best deals; the three major players are

Dr. Solomon's, McAfee's Virus Shield and Norton Antivirus

. Be sure that the operating system you're using, such as Windows '95, iscompatible with the program you choose. Once you get your software, make sureyou update it at least once a week, and that you have it set to scan for viruseswhen your computer boots up. Most of these programs have an "autoupdate"

feature that you can schedule to automatically update your software any time thecomputer is on, even if you're not home. If a particularly notorious virus has beenreleased recently, update it daily for about a week. It may be a pain, but it's worth

it; Symantec, the creator ofNorton Antivirus, estimates that over 5 new virusesare created a day. Two days after the Love Virus was released, over 29variations of were in circulation.
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Update your other software regularly as well. Microsoft released a "patch" in

response to the Love Virus transmission. Software companies

such as Microsoft are constantly discovering new security holes and fixes forbugs in their software. If you're a registered software user, then you can get

these fixes for free by visiting the website or calling their technical support phonenumber. In addition to giving you added virus protection, these security patcheshelp your programs run more smoothly in the long run.

For added protection, and to save a lot of frustration in the long run, it's a goodidea to have a backup of your computer files, just to be on the safe side. A Zipdrive is a great tool for this, but if you don't want to spend the cash, there are lotsof "servers" on the Internet that help you to backup and store files. You can try

one for thirty days free at www.ebackup.com. In addition to backing up yourfiles, you should also check your hard drive to make sure that your computerprogram files (such as .exe and .com) are "read-only." (Your operating system

manual has instructions if you're not sure how to check the Properties.) If acomputer virus tries to access them, you'll get a message to tip you off that thecomputer is trying to change the file.
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23456789 10 Next

Virus ABCs

One of the biggest fears amongnew computer users is beinginfected by a computer virus orprograms designed to destroytheir personal data. Viruses aremalicious software programs thathave been designed by othercomputer users to causedestruction and havoc on acomputer and spread themselvesto other computers where theycan repeat the process.

Once the virus is made, it is oftendistributed through shareware,pirated software, e-mail, P2Pprograms, or other programswhere users share data.

# A B C D E FG H I J K L MN O P Q R S TU V W X Y Z

COMMON VIRUSESTHIS MONTHS VIRUSES

A computer virus is a softwareprogram that was first written Rich Skrentain 1982 who was a 15-year old high school student. Known as The ElkCloner this virus spread to other computers by monitoring the floppydrive and copying itself to any floppy diskette that was inserted into thecomputer. Once a floppy diskette became infected it would infect allother computers that disk was inserted into, each computer that wasinfected would then infect every floppy diskettes inserted into it. Acomputer that was infected would also display a short poem on every50th boot.

Computer users can help protect themselves against computer viruses,malware, and other computer security threats by installing an antivirusprotection program.

Also see our virus question and answer section for other commonquestions about computer viruses.
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How computer viruses are contracted

In the past the majority of computer viruses were contracted from userssharing data using floppy diskettes. However, with the increasedpopularity of the Internet most computer viruses are contracted today

through e-mail and by downloading software over the Internet or P2Psharing.

See document CH001045 for additional information about how yourcomputer could become infected with a virus.

Virus properties

Below is a listing of some of the different properties a computer virus iscapable of having and what the particular property is capable of doing.Keep in mind that not all viruses will have every one of these abilities.

Your computer can be infected even if files are just copied. Becausesome viruses are memory resident, as soon as a diskette or program isloaded into memory, the virus then attaches itself into memory and thenis capable of infecting any file on the computer you have access to.

Can be Polymorphic. Some viruses have the capability of modifying theircode, which means one virus could have various amounts of similarvariants. This is also true with e-mail viruses that change the subject orbody of the message to help from being detected.

Can be memory or non-memory resident. As mentioned earlier a virus iscapable of being either memory resident where the virus first loads intomemory and then infects a computer or non-memory resident where thevirus code is only executed each time a file is opened.

Can be a stealth virus. Stealth viruses will first attach itself to files onthe computer and then attack the computer; this causes the virus tospread more rapidly.

Viruses can carry other viruses. Because viruses are only softwareprograms a virus may also carry other viruses making the virus more lethal

and help the primary virus hide or assist the primary virus with infecting aparticular section of the computer.

Can make the system never show outward signs. Some viruses can hidechanges made, such as when a file was last modified making the virusmore difficult to detect.
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Can stay on the computer even if the computer is formatted. SomeViruses have the capability of infecting different portions of the computersuch as the CMOS battery or master boot record. Finally, if a computer iscompletely erased and the virus is on a backup disk it can easily re-infectthe computer.

How viruses may affect files

Viruses can affect any files; however, usually attack .com, .exe,.sys, .bin, .pif or any data files - Viruses have the capability of infectingany file; however, will generally infect executable files or data files, suchas word or excel documents that are opened frequently and allow thevirus to try infecting other files more often.

Increase the files size - When infecting files, virtues will generallyincrease the size of the file; however, with more sophisticated viruses

these changes can be hidden.

It can delete files as the file is run - Because most files are loaded intomemory, once the program is in memory the virus can delete the file usedto execute the virus.

It can corrupt files randomly - Some destructive viruses are not designedto destroy random data but instead randomly delete or corrupt files.

It can cause write protect errors when executing .exe files from awrite protected disk - Viruses may need to write themselves to files that

are executed; because of this, if a diskette is write protected, you mayreceive a write protection error.

It can convert .exe files to .com files - Viruses may use a separate file torun the program and rename the original file to another extension so theexe is run before the com.

It can reboot the computer when executed - Numerous computerviruses have been designed to cause a computer to reboot, freeze, orperform other tasks not normally exhibited by the computer.

What viruses may do to a computer

Below are different issues you may experience when you are infectedwith a virus. Keep in mind that you also may be experiencing any of thebelow issues by another computer related issue and not a virus.

Deleted files. Various messages in files or on programs.
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Changes volume label. Marks clusters as bad in the FAT. Randomly overwrites sectors on the hard disk. Replaces the MBR with own code. Create more than one partition.

Attempts to access the hard disk drive, which can result in errormessages such as: Invalid drive specification. Causes cross-linked files. Causes a "sector not found" error. Cause the system to run slow. Logical partitions created, partitions decrease in size. A directory may be displayed as garbage. Directory order may be modified so files, such as COM files, will start at

the beginning of the directory. Cause Hardware problems such as keyboard keys not working, printer

issues, modem issues etc.

Disable ports such as LPT or COM ports. Caused keyboard keys to be remapped. Alter the system time / date. Cause system to hang or freeze randomly. Cause activity on HDD or FDD randomly. Increase file size.

Computer Viruses

Boot Sector viruses: A boot sector virus infects diskettes and hard drives. All disks and hard

drives contain smaller sections called sectors. The first sector is called the boot. The boot carries

the Mater Boot Record (MBR). MBR functions to read and load the operating system. So, if a

virus infects the boot or MBR of a disk, such as a floppy disk, your hard drive can become

infected, if you re-boot your computer while the infected disk is in the drive. Once your hard drive

is infected all diskettes that you use in your computer will be infected. Boot sector viruses often

spread to other computers by the use of shared infected disks and pirated software applications.

The best way to disinfect your computer of the boot sector virus is by using antivirus software.

Program viruses: A program virus becomes active when the program file (usually with

extensions .BIN, .COM, .EXE, .OVL, .DRV) carrying the virus is opened. Once active, the virus

will make copies of itself and will infect other programs on the computer.

Multipartite viruses: A multipartite virus is a hybrid of a Boot Sector and Program viruses. It

infects program files and when the infected program is active it will affect the boot record. So the

next time you start up your computer it'll infect your local drive and other programs on your

computer.
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Stealth viruses: A stealth virus can disguise itself by using certain tactics to prevent being

detected by antivirus software. These tactics include altering its file size, concealing itself in

memory, and so on. This type of virus is nothing new, in fact, the first computer virus, dubbed

Brain, was a stealth virus. A good antivirus should be able to detect a stealth virus lurking on your

hard drive by checking the areas the virus infected and evidence in memory.

Polymorphic viruses: A polymorphic virus acts like a chameleon, changing its virus signature

(also known as binary pattern) every time it multiples and infects a new file. By changing binary

patterns, a polymorphic virus becomes hard to detect by an antivirus program.

Macro Viruses: A macro virus is programmed as a macro embedded in a document. Many

applications, such as Microsoft Word and Excel, support macro languages. Once a macro virus

gets on to your computer, every document you produce will become infected. This type of virus is

relatively new and may slip by your antivirus software if you don't have the most recent version

installed

a computer virus is a computer program that can copy

Documents