An Introductory Guide To Malicious Software

Posted: 16 Aug 2017

An Introductory Guide To Malicious Software

Malicious software, otherwise known as malware, is a piece of software or a program that, once installed on a computer, can harm or corrupt the device.

Viruses, worms, Trojan horses and spyware are all various types of malware and can be detrimental to your computer system once installed. With this in mind, malicious software is still something that most people will come into contact with due to the sheer quantity of potentially damaging files on the internet. Here, we look at some of the different types of software and how they work:


Malicious software comes in many different varieties, and it is important that you can recognise each one as it will minimise the time spent trying to remove it from your system.

Probably the most widely recognised form of malicious software is the virus. Much like an illness, such as the common cold or flu, the main purpose of a computer virus is to duplicate and spread, with its eventual aim to infiltrate several computers across a network. This is made possible by the way the virus attaches to the computer.

There are many different types of viruses, such as email viruses and macro viruses. In macros viruses, after the user has downloaded the corrupted file, the virus finds a program that is already existing on your device that uses macros, such as Microsoft Word. The reason the virus will latch onto a macros-enabled piece of software is due to it being written in a similar language. This language is embedded in the infected document and once the program, for example, Microsoft Word, is open, replaces parts of the program’s code with its own.

Other examples of viruses include; resident viruses, which install as part of the operating system in order to re-route functions; email viruses which spread through email attachments; and boot sector viruses, which often require a full system format in order to remove the infection from the master boot record.

The main purpose of the virus can vary due to what the creator wanted it to do. However, some viruses come with disastrous consequences and have the ability to completely wipe devices of their data and files. In some extreme circumstances, they can also alter running processes and have the capability to prevent computers from booting up.


A worm is similar in format to a virus in the way it replicates in order to spread. However, they often work by targeting the soft point of the computer network and travel through the vulnerable areas from one host to another. Worms are a self-contained program, which means that it doesn’t need to attach itself to an executable file in order to work and do not need anything to open them in order for them to be activated. Once in the network, the worm can work in the same way as a virus and has the ability to cause just as much damage.

There are several different ways in which worms attempt to infect networks and systems. One of the most popular ways of worms spreading is through emails. How this works is that a worm will utilise the mass-mailing function of an email account to send emails including an infested attachment across all the addresses in someone’s inbox. Most worms require no participation from the user, so they often spread without knowledge.

Other examples of worms include multiple vector worms, that spread through more than one way. There are also network worms which attempt to infiltrate computer networks over a short period of time and internet worms, which are spread through utilising open ports on the internet.

Trojan Horse

The malicious, Trojan horse software takes its name from a Greek story that took place during the Trojan War. In the story, a large, wooden horse was carefully created by the Greeks to enter the city of Troy. Inside was an army of Greek soldiers who escaped once inside the city walls, allowing the Greeks to win the war. A malicious piece of Trojan Horse software copies this concept and manages to subterfuge users by pretending to be something that it’s not.

Upon receiving the file, the user is led to believe that it is a normal file. However, when opened, the Trojan horse can take control of the user’s computer and has the ability to corrupt and wipe data from the device. One of the ways in which Trojan horse software works is by lingering on the device for extended periods of time. As the malware doesn’t replicate and share, they can sit dormant and find loopholes in the security of your computer.

There are several different types of Trojan’s. One of these is a backdoor Trojan, which is dangerous as it allows a portal to provide access for the attacker. As a result of this, more malware can be uploaded to the computer and can place corrupt files onto the machine. Downloader Trojan’s intent is to keep downloading infected software onto the user’s device, and a remote access Trojan can give the Trojan’s creator to take over the full control of the computer.


Spyware is another form of malicious software that targets a user’s computer without them being aware. Much like a Trojan horse, the software is often installed on the user’s device. However, the main purpose of spyware is to gather information about the victim’s internet usage. The program then secretly records the user’s movement across the internet, either for advertising purposes or for something more malicious, such as for banking passwords and log-in details.

Spyware, due to it often being installed unknowingly, is hard to detect on a user’s computer, which is how it collects that data that it needs to hack accounts. The majority of the time it is installed as an additional extra when downloading from file-sharing sites. The personal information collected by the piece of malicious software is then passed on to third parties and spread.

Classically, there aren’t too many different varieties of spyware, and they often have similar functions. For example, keyloggers record each button on the keyboard that is pressed. This can be useful for hackers due to recording passwords and other important information, such as email addresses. Chat loggers and email recorders do just as the name suggests by keeping a copy of all of your conversations. Lastly, internet loggers and screen recorders track all of your computer movements, by keeping a copy of each of the URL’s that your device visits.

With so many different types of malicious software on the internet, it is necessary for there to be people who have knowledge on all of the different varieties of malware. If you have a specialist knowledge of cybersecurity and want to find appropriate it security jobs, have a browse on our website to find more information on the best cybersecurity jobs in Ireland.

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