Antivirus Reviews: Pick And Choose What Is Best For Your Computer

Anti virus software consists of computer programs that attempt to identify, thwart and eliminate computer viruses and other malicious software (malware). Most commercial antivirus software uses both of these approaches, with an emphasis on the virus dictionary approach. Historically, the term antivirus has also been used for benign computer viruses that spread and combated malicious viruses. This was common on the Amiga computer platform.

To achieve consistent success in the medium and long term, the virus dictionary approach requires periodic downloads of updated virus dictionary entries. As civically minded and technically inclined users identify new viruses in the wild, they can send their infected files to the authors of antivirus software, who then include information about the new viruses in their dictionaries.

Dictionary based antivirus software typically examines files when the computer's operating system creates, opens, closes or emails them. In this way it can detect a known virus immediately upon receipt. A System Administrator can typically schedule the antivirus software to examine all files on the user's hard disk on a regular basis. Although the dictionary approach can effectively contain virus outbreaks in the right circumstances, virus authors have tried to stay a step ahead of such software by writing oligomorphic, polymorphic and more recently metamorphic viruses, which encrypt a part of them or otherwise modify themselves as a method of disguise, so as to not match the virus's signature in the dictionary.

Some antivirus software uses other types of heuristic analysis. For example, it could try to emulate



the beginning of the code of each new executable that the system invokes before transferring control to that executable. If the program seems to use self modifying code or otherwise appears as a virus, one could assume that a virus has infected the executable. However, this method could result in a lot of false positives.

Yet another detection method involves using a sandbox. A sandbox emulates the operating system and runs the executable in this simulation. After the program has terminated, software analyzes the sandbox for any changes which might indicate a virus. Because of performance issues, this type of detection normally only takes place during on demand scans. Some virus scanners can also warn a user if a file is likely to contain a virus based on the file type.


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