A computer virus is a software program that affects the operation of the computer and can potentially damage it. A computer virus is attached to a program or file that allows it to spread from one computer to another while the program is running. Most viruses are attached to an executable file that allows the virus to remain on the computer but cannot cause any damage until you open or run the infected program. Viruses are capable of corrupting or deleting data from the computer. They can also infect other computers. Viruses can enter your computer in different ways, such as through email attachments and infected programs. You won't realize a virus exists until it has caused damage. Different types of viruses cause different types of effects. It is important to learn about these types of viruses and their effects so you know how to prevent and avoid them. These are just a few of the many types of viruses detected. Boot viruses – They only infect the main boot records of the hard drive. The boot recorder is what loads the operating system at startup. These viruses overwrite the startup disk and move it elsewhere on the hard drive. Once the virus is in boot memory, it will do whatever it was originally programmed to do. Program viruses – These types of viruses attack executable files. Files with extensions such as .BIN, .COM, .EXE, .OVL and .DRV. Once the files are executed, the programs and viruses will all be loaded into memory. Once in memory, the virus can spread to other files and cause damage. Fortunately, these are easy to remove compared to startup viruses. Stealth Viruses – These are the expert type of viruses to avoid detection using various methods. Although the middle of the paper is very important because viruses often travel on email attachments and enter the system when you open the attachments. Only open attachments when you have asked someone to send them to you personally. You should also try to avoid downloading from sites and if absolutely necessary, make sure that the website you are downloading the content from is reliable. Although the items listed above are very crucial, it is important to have an antivirus program and keep it updated. something to pay close attention to. This is beneficial because it detects and helps eliminate the virus before it can cause much damage. Make sure you choose a well-known antivirus program. Installing a firewall helps prevent intruders such as viruses from entering. If you have a Windows product, the firewall is enabled by default. Otherwise, make sure to enable the firewall.