Introduction to the antivirus protection - What is a computer virus and what is not

Computers are threatened not only by viruses but also by other malicious codes. Antivirus programs detect most of them. But there often appear different phenomena in computers that cannot be classified as malicious codes - malware (malicious/malign software).

  • Computer virus - It is a piece of a program code that is able to make copies of itself through the host application more than once. In a plain language: Virus is a computer program that spreads without letting know the user sitting at the computer. It has no other property. It does not need to do harm, it does not need to call anybody's attention to itself, which are examples of extra symptoms that their authors add for various reasons.
  • Trojan horse - It is in fact any computer program, which on one hand does what the user is expecting it to do, but on the other hand does something that the user has no notion of and that she or he probably would not agree with. Let us give you an example: some dubious software downloaded from Internet - when you execute it, you can take pleasure in watching a beautiful African dancer, but the same program can be sending files from your computer at the moment (and we certainly do not need to emphasize that it makes no difference between private data and less private data - it is just a dull program) or encrypting some data and consequently asking for a kickback for the code.
  • Backdoors - As the name of this software suggests, these are applications that "open" the computer (without warning the user) for the attackers, who are interested in the data stored on it or in your computer as a tool for their future attacks. More than a type, this is a software property. Genuine backdoors occur very seldom, more likely they are combined with another application type, for example Trojan horses or computer viruses.
  • E-mail worms - It is a slight exaggeration to say that it is a computer virus that uses e-mail services for its spread. But it is not as simple as that. While a computer virus needs host applications for its spread (with the exception of so-called accompanying viruses, which adopt the name of exe files, but they have the com extension and "presume" on the fact that this extension is preferred by operating systems), an e-mail worm is generally malicious itself (there are more exceptions indeed - for example the macrovirus Melissa uses e-mail for its spread) and needs no "host".
  • Funny programs - It is perhaps a strange category among the other malicious codes, but it belongs here. Most of the funny programs behave in a way that they are impossible to quit correctly and hard restart is unavoidable. It may cause fairly serious problems to machines that should run non-stop. That is why antivirus programs are often set to detect these undesirable codes.

Therefore viruses and other malicious programs are detected by antivirus programs. When operating computers, the following problems can be met frequently:

  • Programming errors - In spite of the fact that programmers do their best to test and check their work, sometimes an error or omission occurs. The more complicated and complex software, the higher probability of an error, of course. That is why sometimes a computer program disobeys its owner without any obvious reason. It can be due to a virus, but not necessarily.
  • Software or hardware collision - Yes, it is like that. Even computer programs compete with each other for the free system resources or battle against the lack of capacity (for example, free disk space). Apart from the fact that the most hardware, despite the one hundred percent compatibility declared, is much less compatible. These breakdowns are often adjudicated to the effects of malicious codes (according to the motto "the reason is unknown, there must be some virus behind it").
  • Hardware failures - Another very often "defect" that we can come across in the world of information technologies. Harddisk failures may lead to irrevocable loss of data (backup, backup and once more backup!), but it is not always the consequence of a malicious code attack. Moreover, viruses are not able to damage the hardware physically (even if they can "simulate" its defect). So if you see some strange colors on the screen, first check the graphic card and its functionality - sooner than you start to revile the virus authors or the antivirus software developers.
  • Software damages - A software damage (being a typical sign of computer viruses) can be caused by many other ways. For example an incorrect program can terminate (for example due to short-term power cut) during saving data file. Not every data or software damage is a result of a work of a computer virus. But it is convenient to be cautious so scan the computer properly and try to find the source of problems at any rate. At least in order to avoid the same situation in the future.
  • False alarms - The illness of all antivirus programs. Despite there are less and less false alarms (situations, when the scanning program classifies a clean file or area as infected or suspicious), they will never disappear. "False alarms" are sort of the tax on security, when the antivirus software developers try to reach the optimal price/performance ratio. (in this case it is more the scanning quickness/user's security ratio).

Related references

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Introduction to the antivirus protection