Viruses, Worms, And Trojans – A Basic Guide To Malware

An overwhelming majority of tech users mistakenly attribute the term “virus” to virtually any category of malicious software. In reality, a virus is only one of the various existing subsets of malicious digital menaces that exist today.

Three of the most common types of malicious software – viruses, trojans, and worms – are noticeably different in the methods that they use to attack your digital resources. All three of them fall under the umbrella-like term: malware; which is a portmanteau of “malicious software”. However, virtually all antivirus software worth mentioning will be able to rid your device of these three types of malware (if it doesn’t, it’s time to get a new antivirus program).

Not to be confused with Spyware and Spy Software – again, different problems to worry about! You can check out more information about spy software here.


So what does a virus do? Well similarly to its namesake, the biological virus (which infects cells), a computer virus seeks to infect uncontaminated files. If you have an infected file on your device, once you open/run that file the virus activates and tries to infect uncontaminated files on your device.

One of the most common file types that a virus will try to attach itself to is an .exe file. These are the files that execute whenever you open a program on your computer, so the virus will activate concurrently with the program. Viruses may also seek out documents, such as Word of Excel files. These files are commonly shared with other users via USB devices, emails, etc.; this serves to prolong the lifespan of a virus and ensure that it propagates or “reproduces” onto another device.

Viruses can get a lot worse. At times they may even succeed at going further than simply attaching themselves to a file – they may completely replace it (deleting it and masquerading as it). Last but not least, they can corrupt your system by obfuscating and using up your system memory, leading to crashes and malfunctions.


So what does a worm do? Worms differ from viruses in a few ways. Firstly, they never actually need to be activated by users so that they can spread – they are standalone software. Secondly, they don’t actually try to infect files on your device, their main goal is to replicate themselves and distribute these copies.

For some worms (e.g. Mydoom) this may mean that they copy themselves and make an attempt to email themselves to your contacts. Some worms (e.g. Blaster) are more tenacious, they may abuse the weaknesses in unprotected networks by infecting connected systems that have weak firewalls that they can bypass. These worms can essentially slow a network to a standstill by creating an immense traffic load.

However, just like a virus, a worm can carry out the same malevolent activities once it breaches your system’s protections.


So what does a trojan do? Now most people are familiar with the story of the Trojan horse – the giant wooden horse that the Greeks gave to the Trojans under the guise of gift.malware_trojan_121 However, it wasn’t a gift, inside the horse were Greek soldiers who facilitated the destruction of Troy once they were safely inside the gates. Trojan malware are exactly like their namesake. Trojans act like legitimate useful software; however, once they have been added to your system they open a “backdoor” and let the invaders into your system. One of the most common things that they do is add your system to a botnet so that it can be utilized to perform nefarious deeds. They can even use this connection to add other malware to your device or system. Trojans will virtually never try to spread themselves, they will instead act innocent and hide in the shadows – waiting to strike.

What Else Is There?

Sadly, this isn’t all that here is in terms of types of malware. Some other common malware types are:

Scareware –

This is commonly found on popular web pages, it takes the form of a notification that claims that your system is infected or at risk and that you should download a linked antivirus program to clean your system or remain safe. This is a lie. Most of them will request payment and ask that you give your credit card number – this is a big red flag! It will also latch onto your system and try to stay there until you pay up or purge it.

Spyware –

This does exactly what it says on the tin: It spies on your actions. This can be something as simple as a key logger; software that records your keystrokes so that it can steal valuable information such as passwords and credit card information. Spyware can also be advertising software that observes your internet based activity and reports back to its creators. Spyware can sometimes fly under the radar of some antivirus programs, so do a bit of research to find out just what exactly your antivirus looks for and finds – Windows Defender has been known to be able to root out numerous cases of spyware.

Is there anything essential that we left off? Want to find out more about malware and the dangers they pose to your system? Ask away in the comments below!

David Alexander

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