Explained: What is a computer worm and how it is more dangerous than a virus – Times of India

When we say that a PC or a phone has got a virus, is it the same as saying that it has a worm? No. Both are forms of malware but are very different from each other.
Malware is a malicious software created to infect a host system and damage or gain unauthorised access to it with ill-intent. Malware is a broad category of such softwares and its types are virus, Trojan, worms, adware, spyware, ransomware etc.
In this article, we will lay out the key differences between a computer worm and a virus.
Computer virus
Let’s begin with a computer virus, which is one of the most common forms of malware out there. A virus needs a host to spread, which could be an executable file, a document or any other program. It needs a host to self-replicate so that it could spread the infection throughout the system. It does so by inserting its code into another computer program or an operating system code, which then modifies that program and thus infects it. Having a host is necessary for a computer virus for self-replication. And also, since it cannot act on its own, it needs a necessary action by the user to trigger it. For example, when the user of the targeted device clicks on/executes the infected file, the virus can then cause damage to that particular system.
Computer worm
A worm also infects your system but it does not need a host to spread, meaning it is a self-sufficient program. It self-replicates too but does not need the user to open or activate a certain infected file to program for it to begin laying waste to the system. Also, it does not stay confined to a particular system but rather spreads quickly through a computer network, spreading to other systems on that network as well, thus proving more dangerous and devastating on a larger scale.
A few ways a computer worm can enter your system are via emails, instant messaging apps and the internet in general. A worm can also arrive undetected into your system by exploiting a security vulnerability. You will not even know it and it would already have begun its work in the background.
Computer virus versus worm: Key differences
In short, you need to wake up a virus but not a worm for it to begin its journey of system damage. A computer worm can hence, spread a lot quicker than a virus and in some cases, it can spread to other devices at an exponential rate. An example would be a worm affecting all your email contacts, and then spreading to the contacts of your contacts, thus creating an exponential rate of infection.
So, based on what we have discussed till now, a computer worm can spread faster than a virus, could infect more devices than an average virus and could be usually deadlier too.
A virus will generally not spread to other systems via networks but a worm will. A virus will need human activation to get triggered but a worm does not. A worm will automatically start infecting the files in a system and spreading through them.
The severity levels of infection
The severity levels of a virus/worm attack range from activating unwanted pop-ups or messages on someone’s personal system to nationwide cyberattacks. One example of a computer worm is the WannaCry ransomware worm that spread through a network of computers, infecting thousands of systems on an hourly basis. Such an attack is an example of what is known as a blended threat, where cybercriminals combine the malware types to attack other systems. In the case of WannaCry, it was a double salvo of ransomware and computer worm.