system must have security some programming languages are system independent and some system dependent but while coming to security system independent are high secure rather than system dependent so to avoid from virus to our co9nfidential information system which we are using must be higyhly secured.There are four levels at which a system must be protected: Physical - The easiest way to steal data is to pocket the backup tapes. Also, access to the root console will often give the user special privileges, such as rebooting the system as root from removable media. Even general access to terminals in a computer room offers some opportunities for an attacker, although today’s modern high-speed networking environment provides more and more opportunities for remote attacks. Human - There is some concern that the humans who are allowed access to a system be trustworthy, and that they cannot be coerced into breaching security. However more and more attacks today are made via social engineering, which basically means fooling trustworthy people into accidentally breaching security. Phishing involves sending an innocent-looking e-mail or web site designed to fool people into revealing confidential information. Dumpster Diving involves searching the trash or other locations for passwords that are written down. Password Cracking involves divining users passwords, either by watching them type in their passwords, knowing something about them like their pet’s names, or simply trying all words in common dictionaries. Operating System - The OS must protect itself from security breaches rather than other systems so all are using os as their system software.http://www.pysoft.com