The virus attacks on computer have been there since long time and most of us have faced it at some point of time. Starting with the basic definition a virus in computers can be a program or programming code that replicates by being copied to computer boot sector or document. Viruses can be transmitted as attachments to an e-mail note or in a downloaded file, or be present on an external drive or CD. The immediate source is downloaded file you've received is usually unaware that it contains a virus.
The common symptoms of a computer infected by virus are mainly seen by reduced performance; unknown operations working in the back ground, task manager do not work properly, cases of computer as well as operating system crashes increase significantly. The symptoms depend upon the sources code of the attacking virus. The performance is greatly reduced. Many operations which are unknown to the user run in the computer, windows task manager is disabled .Disk space gets reduced suddenly. Many other unwanted messages are displayed.
Though there are hundreds of antivirus software available but most of them are either paid antivirus or only their trial versions are available. Of all the antivirus we have tried, we found that Norton internet security 2010 in paid version and AVG and Panda antivirus are best free versions on the basis of their capability to clean up the system and the load it puts on computer.
Types of antivirus includes cloud antivirus which is able to send programs or documents to a network cloud where it uses multiple antivirus Or we can put in Network Firewalls which prevent unknown programs and Internet processes from accessing the system protected. However, they are not antivirus systems as such and thus make no attempt to identify or remove anything. Other options include Online Scanning and editing registry.
However, antivirus decreases system's performance and operational speed.
In subsequent years major threat will be from network viruses. It is now only in the earliest state of developments. This type of virus make their first faint attempts to spread their code by themselves via Microsoft Mail and using FTP, but the best is yet to come.