In today's world your computer will be exposed to viruses which CAN harm not only your computer, but it can also send viruses to and potentially infect your friends’ and associates’ computers as well. Whenever you are using a high-speed connection such as ResNet, your computer is connected to the Internet as long as it is turned on, not just when you're actively using it, making it a possible target for break-in.
Whenever connected, it is possible for an intruder to access personal documents on your computer, steal your account and password information for other systems or steal any private information you have stored. Intruders can also use your computer to break into other computers, send out unsolicited mass email, and spread viruses. Viruses, spyware and worms can cause your computer's performance to become slower, use up your disk space, and may allow personal information on your computer to be sent to people whom you do not know. The computer may become unstable, and may require frequent reboots.