What are viruses?
Viruses are computer programs that, when executed, work without your knowledge to destroy data on or execute unwanted commands on your computer. Like their namesakes, computer viruses attach themselves to files on your computer, affect your PC’s performance and replicate themselves. At their least harmful, viruses can cause annoying glitches and some data loss. At their worst, they seek out critical system files and modify or corrupt them affecting the system’s performance and often disabling it, or they can search your computer for certain information (logins, passwords, account numbers, e-mail addresses) and send them to a remote user.
Viruses are very small organisms — most cannot even be seen with an ordinary microscope. They cannot reproduce on their own; they must enter a living cell, which becomes the host cell, and “hijack” the cells machinery to make more viruses. Viruses can enter the body through the nose, mouth, or breaks in the skin. Once inside, they find their specific type of host cell to infect. For example, cold and flu viruses specifically attack cells that line the respiratory or digestive tracts. The human immunodeficiency virus (HIV) infects the T-cells and macrophages of the immune system. HPV infects squamous epithelial cells in the body.
Viruses are the cause of colds and the flu. The same is true for computers. A computer virus spreads by making copies in a host. If a file or program contains a virus, it is infected, and the infected file or program is a host. Typically, a virus is transmitted by attaching itself to an executable program that is emailed to someone. When the recipient clicks on the infected program, the virus is activated and may attach itself to other executable files on the computer. Some viruses can destroy data and wreak havoc with a computer system. Others are simply annoying. The primary danger with viruses is their self-replicating quality, which can take over resources in your computer. Viruses are one of the most commonly known types of malicious software. Other types are worms and Trojan horses. A worm is similar to a virus, but is an independent program that does not need to be attached to another.
Viruses are very small organisms — most cannot even be seen with a regular microscope. They cannot reproduce on their own. They must enter a living cell, which becomes the host cell, and “hijack” the cell’s machinery to make more viruses. Viruses can enter the body through the mucous membranes, such as the nose, mouth, the lining of the eyes, or the genitals. They can also enter through breaks in the skin. Once inside, they find their specific type of host cell to infect. For example, cold and flu viruses find and invade cells that line the respiratory tract (nose, sinuses, breathing tubes, and lungs). The human immunodeficiency virus (HIV) infects the T-cells and macrophages of the immune system. HPV infects squamous epithelial cells in the body — the flat cells that line the surface of the skin and mucous membranes.
Viruses are organisms that are even smaller than bacteria. Although the size of viruses varies the thickness of an average human hair is approximately 1000 times bigger than a virus. See the SMAC report for more details. Viruses consist of just a string of genetic material (DNA) that is contained by a shell known as the ‘viral coat’. They are not cells and they border on being non-living infectious agents as they are only active when in a host cell. Viruses can only replicate (produce more viruses) using the machinery of the cell. This could be a bacterium, plant cell or human cell depending on the type of virus.
