Different Types of Malware and How They Work

Different Types of MalwareMalware is a collective term used to represent virus, worms, spyware and other malicious programs out there on the Internet. In simple words, any software program that is intended to cause direct or indirect harm to the computer system is referred to as a malware.

Some malware programs cause serious problems such as destroying the system files, causing disruption to the computer operation or gathering sensitive information while others may only have a light impact such as redirecting websites to pornographic content or annoying the users with pop-ups and banners.

In the normal routine, we have often seen every malicious program being referred to as a virus, but this is not correct! In fact, as mentioned earlier, there exists several malicious programs where virus is one among them. Now, many of you may be wondering to know what’s the difference between them. Well, this article gives a detailed information on different types of malware that exist, how they work and how they differ from each other:

Computer Virus:

As we all know, this is the type of malware that has become highly popular and is one of the most widely discussed topic in the field of computer security. A virus is just a computer program that is designed to take unauthorized control of the infected computer so as to cause harm to the system’s data or degrade its performance.

Mode of operation:

Computer viruses operates by attaching themselves to an already existing file or program and replicates itself to spread from one computer to another. In most cases, they tend to infect executable files that are parts of legitimate programs. So, whenever the infected file is executed on a new computer, the virus gets activated and begins to operate by further replication or causing the intended damage to the system.

A virus cannot perform its task of harming and replication unless it is allowed to execute. This is the reason why viruses often choose an executable file as its host and get attached to them. Viruses are mainly classified into two types:

Non-Resident Viruses: This kind of virus will execute along with its host, perform the needful action of finding and infecting the other possible files and eventually transfers the control back to the main program (host). The operation of the virus will terminate along with that of its host.

Resident Viruses: In case of resident viruses, whenever the infected program is run by the user, the virus gets activated, loads its replication module into the memory and then transfers the control back to the main program. In this case, the virus still remains active in the memory waiting for an opportunity to find and infect other files even after the main program (host) has been terminated.

Damages caused:

Viruses are known to cause destruction of data and software programs. In some cases, a virus may do nothing other than just replicating itself. However, they are responsible for using a large portion of the system resources such as CPU and memory which results in the performance degradation of the computer.

In order to stay protected from a virus infection, you may refer my other post on 12 tips to maintain a virus free computer.

Trojan horse:

A Trojan horse or simply called as Trojan is a type of malicious program that disguises itself as something that is legitimate or useful. The main purpose of a trojan is to gain the trust of the user from the front end, so that it gets the permission to be installed. But, from the back end, it is designed to grant unauthorized control of the computer to the hacker.

Mode of operation:

A Trojan horse do not depend on the host to carry out its operation. So, unlike a computer virus, it does not tend to attach itself to other files. Trojans are often disguised as video codecs, software cracks, keygens and other similar programs downloaded from untrusted sources. So, one has to be careful about those untrusted websites that offer free downloads.

One of the most popular example is the DNSChanger trojan that was designed to hijack the DNS servers of the victimized computers. It was distributed by some of the rogue pornographic websites as a video codec needed to view online content.

Damages caused:

Trojan horses are known to cause a wide variety of damages such as stealing passwords and login details, electronic money theft, logging keystrokes, modify/delete files, monitor user activity etc.


Worms are standalone computer programs with a malicious intent that spread from one computer to another. Unlike viruses, worms have the ability to operate independently and hence do not attach themselves to another program.

Mode of operation:

Worms often use a computer network to spread itself by exploiting the security vulnerabilities that exist inside the individual computers. In most cases, worms are designed only to spread without causing any serious change to the computer system.

Damage caused:

Unlike viruses, worms do not cause damage to the system files and other important programs. However, they are responsible for consuming the bandwidth thereby degrading the performance of the network.


Spyware is a type of malicious software that can collect information about the activities of the target computer without the knowledge of its users. Spywares such as keyloggers are often installed by the owner or administrator of the computer in order to monitor the activities of the users. This can be a parent trying to monitor his child, a company owner trying to monitor his employee or someone trying to spy on his/her spouse.

Mode of operation:

Spywares are designed to operate in a totally stealth mode so that its presence is completely hidden from the users of the computer. Once installed, they silently monitor all the activities on the computer such as keystrokes, web activity, IM logs etc. These logs are stored secretly for later access or uploaded online so that the installer of the spyware program can have access to them.

Damage caused:

Apart from monitoring, spywares do not cause any damage to the computer. However, in some cases the affected computer may experience degradation in its performance.


Adware is a software program that automatically renders advertisements to the users without their consent. Most common examples are pop-ups, pop-unders and other annoying banner ads. The prime reason behind the design of adware is to generate revenue for its author.

Mode of operation:

Adwares are often bundled up with some of the free utilities such as a browser toolbars, video downloaders etc. When such programs are installed, the adware may take over and distract user activity by displaying annoying advertisements.

Damage caused:

Adware is harmless in most of the occasions. However, some are known to contain spywares that are used to monitor the surfing habits of users. This may pose a threat to the privacy of the users.

It is possible to keep the adware at bay by reading my other post on 10 tips to avoid getting adware. I hope you find this article informative and useful. Pass your comments.


  1. Mahaveer
    October 2, 2012 at 1:26 PM

    Old topic but simplified language was the attraction here. Thanks for sharing.

    • Srikanth
      October 2, 2012 at 4:13 PM

      @ Mahaveer

      Thank you for the first feedback :)

  2. rahual
    October 2, 2012 at 8:36 PM

    nice dude you good

  3. rajesh_aslan
    October 2, 2012 at 8:53 PM

    nice post, i read so many times about malware, but i get the real clarity here, thats why i like ur post

  4. Manu14143
    October 3, 2012 at 5:43 AM

    The best way to put things across… Thank You..

  5. Anil Saini
    October 3, 2012 at 10:34 AM

    Very Nice information, never known about these fact. Trojans and spywares are the dangerous ones, can a single antivirus program keep them away?

    • Srikanth
      October 3, 2012 at 1:23 PM

      @ Anil Saini

      Yes, most of the time a single antivirus such as Kasperspy or Bitdefender is enough to offer protection against most malware.

  6. kenhigh
    October 4, 2012 at 3:27 PM

    Any example on how to code them. I need to know how its coded. On any language

  7. jeff
    October 19, 2012 at 11:24 AM

    i need a trojan… anyone who can help me with it i will pay some dollars

  8. Ama
    October 21, 2012 at 3:27 PM

    Nice article, but kaspersky and bitdefender are not free, wat are the best free antivirus softwares that can be used to check this malwares

    • Srikanth
      October 21, 2012 at 6:03 PM

      @ Ama

      You can try Malwarebytes which is a very good anti-malware. Other options include Avira and Avg.

  9. dontspotme
    October 23, 2012 at 6:20 AM


    The BEST anti malware software is MSE .
    You can download it at windows.microsoft.com/mse

  10. Debasish
    December 27, 2012 at 8:08 PM

    I have a problem . I have installed javaME and JDK in my windows7 pc to install java in my china mobile(hitech-HT3600),because I want to install operamini in my mobile. But
    I can not install it ,after moving it in mobilephone drive.when I am doubleclick on it , it warns me that the JAVAME is already installed in my computer if I continue that installation process,the file will be over writen. so, how I can install java in my mobile? please……..help me as a senior .
    thanking you.

  11. Nasim
    January 9, 2013 at 9:35 PM

    Thanks!!!awesome info 😉 appreciate it :)

  12. SIP Softphone
    January 31, 2013 at 3:40 PM

    Interesting and informative post Stop Torture .
    Thanks for helpful article. Me pleasure to read your thinks. Cheers

  13. Bolaji
    February 28, 2013 at 10:00 AM

    9ce Tut. Sir, pls, i want you to tell us how to install Windows and Linux on a hard drive. Thanks

  14. Dave
    March 14, 2013 at 1:50 PM

    Very well set out article. Viruses like the ones you listed can certainly do plenty of damage so it’s important to stay alert and secure against them all.

  15. Gani...
    August 3, 2013 at 11:31 AM

    Nice stuff..

  16. Daniel
    February 17, 2015 at 3:18 AM

    Tnx It realy helped me out a lot
    is there any way i can download a trojan hourse or i have to get it from a hacker????
    (Im Commenting in 2015 LOL)

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