A computer virus is a malware program that, when executed, replicates by inserting copies of itself into other computer programs, date files or the boot sector of the hard drive. When this replication succeeds, the affected areas are then said to be infected.
A computer virus is a malicious program that self-replicates by copying itself to another program. In other words, the computer virus spreads by itself into other executable code or documents. The purpose of creating a computer virus is to infect vulnerable systems, gain admin control and steal user sensitive data. Hackers design computer viruses with malicious intent and prey on online users by tricking them.
One of the ideal methods by which viruses spread is through emails – opening the attachment in the email, visiting an infected website, clicking on an executable file, or viewing an infected advertisement can cause the virus to spread to your system. Besides that, infections also spread while connecting with already infected removable storage devices, such as USB drives.
It is quite easy and simple for the viruses to sneak into a computer by dodging the defense systems. A successful breach can cause serious issues for the user such as infecting other resources or system software, modifying or deleting key functions or applications and copy/delete or encrypt data.
Famous Computer Viruses
- Stuxnet: It is a Microsoft windows computer worm discovered in June, 2010 that targets industrial control systems.
- Malware: It is a malicious software designed to infiltrate a computer system without the owner’s informed consent. Malware’s most common pathway from criminals to users is through the Internet, primarily by e-mail and World Wide Web.
- Botnets: It is a network of private computers infected with malicious software and controlled as a group without the owners’ knowledge, e.g., to send spam.
- Nagware/Begware/Annoyware/Nag scrum: It is a software utility that ‘nags’ users into upgrading or buying a premium version of software by sending constant pop-up messages or notifications. Software developers use Nagware as a marketing tactic to remind users to take advantage of special offers and purchase software.
- Trojan Horse: It is program that appears harmless, but is, in fact, malicious. Unexpected changes to computer settings and unusual activity, even when the computer should be idle, are strong indications that a Trojan is residing on a computer.
- Web Crawler/Spider: It is a program or automated script which browses the World Wide Web in a methodical, automated manner.
- Grayware: It includes applications that carry out unwanted actions, such as tracking user’s behaviour on-line.
- Flame/Flamer/sKyWIper: It is modular computer malware discovered in 2012 that attacks computers running the Microsoft Windows operating system. The program is being used for targeted cyber espionage in Middle Eastern countries.
- Rootkit: It is is a program or, more often, a collection of software tools that gives a threat actor remote access to and control over a computer or other system.
- Firewall: The primary objective of a firewall is to control the incoming and outgoing network traffic by analyzing the data packets and determining whether it should be allowed through or not based on a pre-determined rule set.
The History of Computer Virus
Robert Thomas, an engineer at BBN Technologies developed the first known computer virus in the year 1971. The first virus was christened as the “Creeper” virus, and the experimental program carried out by Thomas infected mainframes on ARPANET. The teletype message displayed on the screens read, “I’m the creeper: Catch me if you can.”
But the original wild computer virus, probably the first one to be tracked down in the history of computer viruses was “Elk Cloner.” The Elk Cloner infected Apple II operating systems through floppy disks. The message displayed on infected Apple Computers was a humorous one. The virus was developed by Richard Skrenta, a teenager in the year 1982. Even though the computer viruses were designed as a prank, it also enlightened how a malicious program could be installed in a computer’s memory and stop users from removing the program.
It was Fred Cohen, who coined the term “computer virus” and it was after a year in 1983. The term came into being when he attempted to write an academic paper titled “Computer Viruses – Theory and Experiments” detailing about the malicious programs in his work.
Types of Computer Viruses
A computer virus is one type of malware that inserts its virus code to multiply itself by altering the programs and applications. The computer gets infected through the replication of malicious code. Computer viruses come in different forms to infect the system in different ways. Some of the most common viruses are,
- Boot Sector Virus – This type of virus infects the master boot record and it is challenging and a complex task to remove this virus and often requires the system to be formatted. Mostly it spreads through removable media.
- Direct Action Virus – This is also called non-resident virus, it gets installed or stays hidden in the computer memory. It stays attached to the specific type of files that it infect. It does not affect the user experience and system’s performance.
- Resident Virus – Unlike direct action viruses, resident viruses get installed on the computer. It is difficult to identify the virus and it is even difficult to remove a resident virus.
- Multipartite Virus – This type of virus spreads through multiple ways. It infects both the boot sector and executable files at the same time.
- Polymorphic Virus – These type of viruses are difficult to identify with a traditional anti-virus program. This is because the polymorphic viruses alters its signature pattern whenever it replicates.
- Overwrite Virus – This type of virus deletes all the files that it infects. The only possible mechanism to remove is to delete the infected files and the end-user has to lose all the contents in it. Identifying the overwrite virus is difficult as it spreads through emails.
- Spacefiller Virus – This is also called “Cavity Viruses”. This is called so as they fill up the empty spaces between the code and hence does not cause any damage to the file.
Antivirus software, or anti-virus software (abbreviated to AV software), also known as anti-malware, is a computer program used to prevent, detect, and remove malware. Antivirus software was originally developed to detect and remove computer viruses, hence the name. However, with the proliferation of other kinds of malware, antivirus software started to provide protection from other computer threats. In particular, modern antivirus software can protect users from: malicious browser helper objects (BHOs), browser hijackers, ransomware, keyloggers, backdoors, rootkits, trojan horses, worms, malicious LSPs, dialers, fraudtools, adware and spyware. Some products also include protection from other computer threats, such as infected and malicious URLs, spam, scam and phishing attacks, online identity (privacy), online banking attacks, social engineering techniques, advanced persistent threat (APT) and botnet DDoS attacks.