A computer virus is a type of malicious software that piggybacks onto valid application code so as to spread and replicate itself. Like other kinds of malware, a virus is set up by attackers to damage or take control of a computer. Its title stems from the method where it infects its aims.
Similarly, a computer virus is not itself a standalone application. It is a code snippet that inserts itself into another application. When that program runs, it executes the virus code, with results that vary from the irritating to the catastrophic. Get in the mind of a hacker, learn their motives and their anti virus. In everyday conversation and the popular media, we frequently use virus and malware interchangeably.
But strictly speaking a virus is a particular type of malware that fits the definition above. The two other main kinds are Trojans, which masquerade as benign applications to trick users into executing them, and worms, which can replicate and spread independently of any other program. The distinguishing feature of a virus is that it ought to infect other programs to function.
Imagine an application in your computer was infected by a virus. (We’ll examine the various ways which may occur in a moment, but for today, let us just take disease as a given.) How does the virus do its dirty work? Bleeping Computer gives a excellent high-level summary of how the method works.
The overall course goes something like this: the infected program implements (usually at the request of the consumer ), and the virus code is loaded into the CPU memory. At this time, the virus spreads itself by infecting other programs on the server computer, inserting its malicious code where it can. (A resident virus does this to apps as they open, whereas a non-resident virus can infect executable files even if they are not running.) Boot sector viruses utilize a specially pernicious technique at this point: they put their code in the boot sector of the computer’s system disk, ensuring it will be implemented even before the operating system fully loads, which makes it impossible to operate the computer at a”clean” way.
When the virus gets its hooks into your computer, it can begin implementing its payload, that is the expression for the section of the virus code which does the dirty.
These can include all kinds of nasty things: Viruses can scan your computer hard disk for banking credentials, log your keystrokes to steal passwords, turn your computer into a zombie that starts a DDoS attack from the hacker’s enemies, or even encrypt your information and need a bitcoin ransom to restore accessibility. (Other kinds of malware may have similar payloads, of course: there are ransomware worms and DDoS Trojans and so on.) In the first, pre-internet days, viruses often spread from computer to computer via infected floppy disks. The SCA virus, for example, spread amongst Amiga users on discs with pirated software. It was mostly benign, but at one point as many as 40 percent of Amiga users were infected.