A virus is a computer program or software that infects a target computer without the person knowing about it. It is a piece of software that uses other real programs to infect. A virus spreads from one computer to another, and can only infect a computer when the program that's infected is executed. The virus is different than denial of service, which is when consumption of computer resources occur. A virus can be located in CD's, dvd's, floppy disks, and usb's. There's an increase chance of getting a virus through a network file system. Sometimes a virus can be confused with computer worms or trojan horse, which are types of malware.
The first virus, the creeper virus, was detected on ARPANET, which was one of the first versions of the internet. The first PC virus happened in 1986 by the Farooq Alvi Brothers in Lahore, Paistan. It was a personal computer virus known as the Brain. Nowadays virus commonly spread through network systems, but back in the day they were spread through removeable media, most commonly the floppy disk.
Viruses' have been a common occurance since the 1980's, but in the 1990's macro viruses popped up. These were viruses that were embedded in word and excels files and destroyed documents and spreadsheets. The only way a virus can affect a computer is when the file that it is located in is executed and embedded into the memory.
There are two types of viruses, resdient and non resident viruses. When infected in a host, the NON RESIDENT virus immediately tries to find other hosts to infect and than finally get into to the application program. A RESIDENT virus, infects a host program and than that is it. It just hangs around and when other software and other executable files try to use that program, they get infected as well.
There are many hosts that a virus can be located in. There are executable files, like microsoft window applications and other portable programs. They can also be located in floppy disks, cd's and dvd's. They can also exist in documents and excel files and well as other batch files. It can be located in usb memory sticks and other databases. PDF and HTML files can contain viruses as well. There are many computer files that a virus can affect, and that what makes it so dangerous. Viruses are also very good at being sneaky and undetected. Some viruses damage files without increasing in size or without actually damaging them. They do this by using space that is unoccupied by the program, so it looks like nothing is wrong. Another way to avoid detection is to make the antivirus program give the request to read the file to the virus, instead of the operating system, this makes the virus undetectable. The virus can also change its code every time it infects another host. This can make the antivirus software harder to detect the virus. A virus can also contain an encryption, that can make it almost impossible to detect.
Anti virus Program are evry important when it comes to finding viruses in a computer system. It detects and tries to eliminate all possible viruses and other malware viruses. There are two way an anti virus progam can detect a virus. he first way is by virus signatures. The program looks at all the contents of the compuetr and than running all the programs against the virus signature. This is a good methid, but onl viruses that are in the deinitions can be detected and the new ones cannot be detected by the viris signatures. The second way is to use different os in different systems, whic can maje it hard for a virus to infect. By making backup, if smething is to happen, you can just use the backuos. The virus probably will not infect both.
There are also way to remove viruses from your computer. You can just unplug your internet cable, because that is a way for viruses to communicate. You should quarantine the virus, and since you have no more internet, it cannot go anywhere, so it will be easier to get rid of it faster. Than install a better anti virus software and than scan again to make sure you do not have anymore.