The viruses are the malicious programs that enable a copy of it self to be embedded in one or more programs. They perform the unwanted tasks. These are the rapidly copy able malicious programs that infect all of the computers attached to a network or the internet. It’s the most common computer infection all over the world.
Nature of viruses
These viruses can do anything but its distinctive feature is it ability to attach itself and execute secretly during the host program runtime. The computer viruses undergo four stages. The first is the dormant stage when it is idle. These programs activate with an event. Not all viruses have a dormant stage. The next stage is the propagation stage when it places its identical copy into another program or hard disk. Each program will propagate with its clone attached to itself. The next stage is the triggering stage when it gets activated to perform its intended task. It is dependent on an event e.g. a specific time to activate it. the last phase is the execution stage. This stage may be harmless or damaging such as destruction of data files.
Types of viruses
There are many types of viruses but some of the most common types are the parasitic virus, memory-resident virus, boot sector virus, stealth virus and polymorphic virus. The parasitic virus attaches itself to executable files and replicates during execution of the files and infects other executable files. The memory resident virus lodges itself into the main memory of a resident system program and infects other programs that execute. The boot sector virus infects the master boot record and spreads when a system is booted every time from the disk containing virus. The stealth virus hides itself from getting detected. The polymorphic virus mutates with every infection.