Key Difference: Worms are standalone computer programs that are considered as a sub-class of a virus. Viruses are programs or codes that attach themselves to files and programs and run inside the computer without the knowledge of the user.

Worms and viruses are two of the many malicious programs that can damage a computer system. The programs were made in order to discover files, programs stored on a user’s or to allow a person easy access to another’s computer. These two types of programs are known as malware and also include ransomware, trojan horses, keyloggers, most rootkits, spyware, dishonest adware, etc. Due to virus being the first type of malware found, many people often refer to all these kinds of malware as virus. However, malware and worm are two different types of malicious programs and work in different ways.

Worms are standalone computer programs that are considered as a sub-class of a virus. In reality, they are a much more effective form of malicious software as they do not require human interaction to spread. Worms have the ability to replicate themselves and infect any part of the computer they find. They can also affect other portable devices that are attached to the computer. It takes advantage of the file or information transport features on your system and uses it to travel on its own.  It has the ability to replicate itself on a computer and send hundreds or thousands of copies of itself through the user’s e-mail address book. It would then replicate on the receiver’s computers and then forward more copies of themselves using the receiver’s address books, resulting in a mass infection. The worm does not infect, alter or delete files; however it does consume system memory causing networks servers, web servers and the computer to stop working. It can also create backdoors in a computer that allows the hackers to easily get access to the computer system. Worms can also cut off access of a user to certain command properties, making it harder to remove them. Many antivirus and spyware software can be used to keep the computer from becoming infected and also removing any available infections. The computer can also be formatted to its original state removing all data including the worm.

Viruses are programs or codes that attach themselves to files and programs and run inside the computer without the knowledge of the user. The term ‘virus’ has become an umbrella term for all types of malware, which have the ability to replicate itself and does not include adware and spyware. Viruses have been termed as virus because of their characters that are similar to actual viruses. They can attach to a certain hosts, files and programs and then replicate themselves to completely infect the computer. They can also travel via transference of data and files to infect other systems. All computer viruses are man-made. Almost all viruses are attached to an executable files, which requires the user to run the file in order for the virus to infect the system.  There are two types of viruses: Nonresident and Resident. Nonresident viruses, upon execution, immediately start searching for other hosts that can be infected, infect those targets, and finally transfer control to the application program they infected. Resident viruses do not immediately search for hosts and instead loads itself into memory on execution and transfers control to the host program. The main purpose of a virus to infect, alter and damage files. These can also change the name and location of the files and corrupt them to the point that they become unreadable. Computers can be protected by using antivirus and spyware software. In order to remove the virus, infected files can be deleted or the computer can be formatted or restored.

Viruses and worms are both harmful for the computer and the security of the user. Worms can provide an easy access to the user’s data, files and IP addresses, while viruses can enable the user to lose information that is stored on the computer. Experts suggest that in order to protect the computer, the user should install spyware or antivirus software, use browsers that protect users from malware by checking the website before allowing access. Also, the users should not open or execute files and programs that they receive from unknown people.

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