Networking Security Security threats can be of many types varing from a simple program that keeps on displaying annoying pop-up ads while your surf, to a malicious program that damages the operating system. Let us study some of the most common security threats. > Virus- A virus is a harmful piece of code that is programmed to cause inconvenience to the user by corrupting or destroying the files in the user's computer. Some of the viruses may even damage the operating system. A virus spreads by creating exact copies of itself and infecting other applications without the knowledge of the user. But it is dependent upon a host file or boot sector to do so. > Worm - A worm is a replicating program that runs independently and spreada through vulnerablities in network services.  The most common method of propagation used by worms is by carrying themselves through email attachment, the worm infect this computer too. > SPYWARE- Spyware is software that is install...