Or, suppose a client sends an e-mail message that doesn't arrive at the agency and a loss occurs. A computer virus is a small software program designed to replicate and spread, generally without the recipient's knowledge. The virus can infect, or become resident, in almost any software module, including an application, operating system, system boot code or device driver. What makes viruses dangerous is their ability to trigger an event. While some events are benign, for example, displaying a message on a certain date, others can be annoying, slowing performance or altering the screen display.
Some viruses even can be catastrophic, damaging files, destroying data and crashing systems.
At the very least, viruses expand file size and slow real-time interaction, hindering the performance of your machine. The intent of many virus writers is only to infect systems, not to damage them. However, because viruses often are flawed, even benign viruses can interact with other software or hardware and slow or stop the system. Other viruses are more dangerous. Viruses come from a variety of sources.