A Computer Virus Is A Computer Program That Can Copy

A computer virus is a computer program that can copy itself and infect a computer. The term "virus" is also commonly but erroneously used to refer to other types of malware, adware, and spyware programs that do not have the reproductive ability. A true virus can only 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 a floppy disk, CD, DVD, or USB drive. Viruses can increase their chances of spreading to other computers by infecting files on a network file system or 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 of malware. 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 worms and Trojan horses, which are 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, like viruses, may cause harm to either a computer system's hosted data, functional performance, 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 usually be: 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

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 can infect 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 of communication today. We send them through the office, to our children, and to our clients. We use it because it is quick and easy. We have electronic address books instead of little black books. Email frauds commit their crimes in a way similar to con artists who commit their crimes over the telephone. How many times have you gotten a phone call from a strange source, asking you for money or personal information? When you asked them 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 viruses prey 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 best time to shop for it! In lieu of the recent virus attacks, many of anti-virus companies are giving away free 30-day-trials. (Just remember the deal is much sweeter when you're downloading it before your computer catches a virus!) You can 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, is compatible with the program you choose. Once you get your software, make sure you update it at least once a week, and that you have it set to scan for viruses when your computer boots up. Most of these programs have an "autoupdate" feature that you can schedule to automatically update your software any time the computer is on, even if you're not home. If a particularly notorious virus has been released recently, update it daily for about a week. It may be a pain, but it's worth it; Symantec, the creator of Norton Antivirus, estimates that over 5 new viruses are created a day. Two days after the Love Virus was released, over 29 variations of were in circulation.

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 for bugs 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 phone number. In addition to giving you added virus protection, these security patches help 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 good idea to have a backup of your computer files, just to be on the safe side. A Zip drive is a great tool for this, but if you don't want to spend the cash, there are lots of "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 your files, you should also check your hard drive to make sure that your computer program 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 a computer virus tries to access them, you'll get a message to tip you off that the computer is trying to change the file.

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Virus ABCs One of the biggest fears among new computer users is being infected by a computer virus or programs designed to destroy their personal data. Viruses are malicious software programs that have been designed by other computer users to cause destruction and havoc on a computer and spread themselves to other computers where they can repeat the process.

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Once the virus is made, it is often distributed through shareware, pirated software, e-mail, P2P programs, or other programs where users share data. A computer virus is a software program that was first written Rich Skrenta in 1982 who was a 15-year old high school student. Known as The Elk Cloner this virus spread to other computers by monitoring the floppy drive and copying itself to any floppy diskette that was inserted into the computer. Once a floppy diskette became infected it would infect all other computers that disk was inserted into, each computer that was infected would then infect every floppy diskettes inserted into it. A computer that was infected would also display a short poem on every 50th boot. Computer users can help protect themselves against computer viruses, malware, and other computer security threats by installing an antivirus protection program. Also see our virus question and answer section for other common questions about computer viruses.

How computer viruses are contracted In the past the majority of computer viruses were contracted from users sharing data using floppy diskettes. However, with the increased popularity of the Internet most computer viruses are contracted today through e-mail and by downloading software over the Internet or P2P sharing. See document CH001045 for additional information about how your computer could become infected with a virus.

Virus properties Below is a listing of some of the different properties a computer virus is capable 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. Because some viruses are memory resident, as soon as a diskette or program is loaded into memory, the virus then attaches itself into memory and then is capable of infecting any file on the computer you have access to. Can be Polymorphic. Some viruses have the capability of modifying their code, which means one virus could have various amounts of similar variants. This is also true with e-mail viruses that change the subject or body of the message to help from being detected. Can be memory or non-memory resident. As mentioned earlier a virus is capable of being either memory resident where the virus first loads into memory and then infects a computer or non-memory resident where the virus code is only executed each time a file is opened. Can be a stealth virus. Stealth viruses will first attach itself to files on the computer and then attack the computer; this causes the virus to spread more rapidly. Viruses can carry other viruses. Because viruses are only software programs 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 a particular section of the computer. Can make the system never show outward signs. Some viruses can hide changes made, such as when a file was last modified making the virus more difficult to detect.

Can stay on the computer even if the computer is formatted. Some Viruses have the capability of infecting different portions of the computer such as the CMOS battery or master boot record. Finally, if a computer is completely erased and the virus is on a backup disk it can easily re-infect the 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 infecting any file; however, will generally infect executable files or data files, such as word or excel documents that are opened frequently and allow the virus to try infecting other files more often. Increase the files size - When infecting files, virtues will generally increase 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 into memory, once the program is in memory the virus can delete the file used to execute the virus. It can corrupt files randomly - Some destructive viruses are not designed to destroy random data but instead randomly delete or corrupt files. It can cause write protect errors when executing .exe files from a write protected disk - Viruses may need to write themselves to files that are executed; because of this, if a diskette is write protected, you may receive a write protection error. It can convert .exe files to .com files - Viruses may use a separate file to run the program and rename the original file to another extension so the exe is run before the com. It can reboot the computer when executed - Numerous computer viruses have been designed to cause a computer to reboot, freeze, or perform 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 infected with a virus. Keep in mind that you also may be experiencing any of the below issues by another computer related issue and not a virus. • •

Deleted files. Various messages in files or on programs.

• • • • • • • • • • • • • • • • • • •

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 error messages 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.

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