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Classification of computer viruses

Classification of computer viruses
Classification of computer viruses
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Big popularity of personal computers and the rapid development of the Internet gave rise to numerous kinds of malware programs - viruses. Viruses often make working on a computer impossible (bugs, glitches, information leaks, system "slowdown"), and sometimes even causes the system to "crash" destroying useful information. Let's try to clarify what is a virus, how to deal with it and what types of viruses we are dangerous.

What is a virus

Computer virus is a specially written program of a small size that can "enter" the body of other programs, take control, and replicate with a specific task - to terminate computer operation and corrupt data. Scary, isn't it?

How does the virus enters your computer

Viruses can get onto your computer's hard disk or RAM: portable data storages - floppy disks, CD's and DVD's, but most enter the computer through the Web.

Most of these viruses are written by individuals or groups of hackers. The result is always the same – operating system crash, loss or theft of crucial information (passwords, keys) regardless of motives behind viruses. In spite the fact that the creating and spreading of this software is illegal in most of the countries, creation of viruses flourishes, and will not go away. At least not in the nearest future. Most viruses infect executable files with exe, com, sys, bat and boot sectors of computer disks.

Classification of viruses

With such a large number of different viruses found in the web it's easy to get confused. Yet computer viruses have their classification. That is...

According to the environment
  • network viruses (they can be distributed through different computer networks);
  • file viruses (infecting executable files - com, exe, bat.);
  • boot viruses (infecting boot sectors or a sector containing the system disk boot program - Master Boot Record);
  • file-boot viruses (act the same as the boot viruses).
According to the method of infecting
  • resident (this virus when infecting PCs leaves its resident part in RAM, which then intercepts requests from OS to targeted objects and infects them. Resident viruses live up to the first reboot of the PC);
  • non-resident (don't infect RAM and may be active for limited time).
By the result of exposure
  • harmless (usually these viruses clog computer memory by their replication and can have a hidden minor prank - play a unwanted melody or show a picture);
  • hazardous (these viruses are capable of creating some irregularities in the operation of your PC - crashes, reboots, glitches, computer slowdown, etc.);
  • very dangerous (dangerous viruses can destroy programs, delete sensitive data, destroy  system and boot areas on your hard drive, which is useless afterwards and can be discarded ).
By working algorithm 
  • parasitic (changes the contents of files and disk sectors. Such viruses are easily calculated and removed);
  • mutants (they are very hard to detect because they use encryption. Every next copy of the virus will not be like the previous one);
  • replicators (viruses replicators, a.k.a. Worms, penetrate the computer networks, find the addresses of the computers in the network and infect them);
  • trojan horse (one of the most dangerous viruses, because Trojans do not replicate, they are stealing sensitive (sometimes very important) information - passwords, bank accounts, e-money, etc.);
  • invisible (these are difficult to detect viruses that intercept requests of OS to infected files and disk sectors and substitute them with non-infected areas.

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