WHAT ABOUT COMPUTER VIRUSES part2

In my last article I've started giving out some useful stuff about viruses.
I 've revealed some advices about how to prevent our computers from them ,and the remaining subject was about the most known" anti-virus software "at the very end of the article.
The following paragraphs will try to give a quick review about the antivirus.

An anti virus software is used to prevent, detect and remove malware,including computer
viruses,worms,trojan horses...,such program may also prevent and remove adware,spyware and other forms of malware.
Now let's try to understand how does the anti-virus software work,the methods which the software use to identify viruses or other malware.

The most common method is the signature based detection, it combines the content of a file to a list of virus signatures as the virus can fix itself in existing files.
This method is more effective in case the malware's sample has already been abtained and signatures created, because of this ,the method isn't effective against unknown viruses,that is why we still have other methods like the malicious activity detection where the antivirus observe the system for suspicious behaviours,the heuristic-based detection and so on.

In order to make a good decision about which software to buy, one can check reviews and ratings on internet,there's also a solution for people who don't want to spend a coin buying anti-virus software as they can download shareware anti-virus programs on the net.

Concluding, I would like to ask for your attention as some problems will accur when using the software,some anti-viruses can reduce performance, that's why the software needs to be enabled all the times as users will decide to disable the anti-virus software protection for regaining the performance ,you may also consider some unexpected renewal costs.