What is a Malicious Program/Malwares? Check the difference between malwares – Virus, Worm, Root Kit, Trojan Horse and Types of Virus

Hi friends, today I am writing about malicious programs – Virus, Root kit, Trojan horse etc and the types of viruses. So, firstly it is very important to know What is malware? It is an important topic for exams like IBPS IT officer, Assistant Manager (IT), SBI IT officer, GIC Officer Scale – I, Computer Teacher, Computer Engineer or any other computer engineer related post.

Looking over the importance of this topic, I am explaining this in detail and will also share a questionnaire on it soon. So stay updated with this website and let me know if you want more on this topic. Let’s first understand what Malicious Program is.

What is Malicious Program/Malwares?

Malicious software, which are commonly known as Malwares are a type of software that can harm your computer system. These programs come in different forms for example: viruses, trojans, worms, spyware, adware, root kit, zombie, key loggers etc.

These programs can delete documents, modify or steal the protected data and also add software to your computer programs which are not approved by user.

Hope you get a basic idea of the dangerous nature of these programs. Now, let’s move to the core concepts of this Malicious Programs section so that IT officer post or any computer science post people can answer the questions related to malicious programs.

Malicious Program

Types and Forms of Malicious Programs

Forms of Malicious Programs
Type/Form of Malicious ProgramDescription
VirusIt attaches itself to a program and propagates copies of itself to other programs and thus harm the data.
WormIt is a program that propagates copies of itself to other computers basically through Network
Trojan HorseIt is a program that contains unexpected additional functionality
Backdoor (Trapdoor)Program that allows unauthorized access to programs and  functionality
Logic BombIt triggers action when a specific condition occurs
ExploitsIt is a code specific to a single vulnerability or set of vulnerability
Auto-rooterMalicious hacker tools which are used to break into new machines remotely
Downloader’sUsually downloader’s are sent in an email. It is a program that installs other items on a machine that is under attack.
Key LoggersIt captures keystrokes on a compromised system. Think a program is stealing your credentials details during a transaction
ZombieProgram activated on an infected machine that is activated to launch attacks on other machines
Root KitThese are Set of hacker tools used after attacker has broken into a computer system and gained root-level access
FloodersFlooders are used to attack networked computer systems with large volume of traffic to carry out a denial of service attach (DoS) attack.
Spammer ProgramsSpammer programs are also a kind of malicious software. These are used to send large volumes of unwanted emails
Kit (Virus Generators)Kit is a set of tools for generating new viruses automatically

I have tried to provide the maximum information that covers most of the questions from Malicious Programs section for government exams. Also, if you want to learn basics of SQL, then follow.

Difference between Computer Virus, Computer Worm, Trojan Horses and Bots

Computer Virus vs Computer Worm :

Computer worms are similar to viruses in the manner that they replicate the functional copies of themselves and can cause the same type of damage. But, still there are some differences in the way these malicious programs cause damage.

In contrast to Viruses, which require the spreading of an infected host file, worms do not require a host file to propagate. Instead, worms are standalone software that do not require any host program or human help to propagate from one computer to another. Now let’s see some basic difference between these malicious programs/malware programs:

Virus :

Computer viruses attach a copy of itself to files or programs, infecting each computer it comes across as it spreads. It usually spreads through Emails or executable files. Some viruses are very annoying because they slow down your computer, while others can wreak havoc on your system. Viruses usually modifies files or it may sometimes change the location of a file.


Computer Worms also replicate themselves but unlike viruses, these malicious programs do not attach themselves to a program. Instead, these spreads from computer network to network and are extremely dangerous.

These can also damage the servers. Computer worms usually do not infect files. Instead these monetize your computer memory or CPU.

Trojan Horses:

These malicious programs are sneaky ones. Trojan horses hides all sorts of malicious goodies and can harm your computer. These malicious programs may look legitimate software at first glance, but when you install these programs they can delete or modify your files.

Unlike viruses and worms, Trojan horses do not replicate themselves.


Bots are a type of malicious programs that may have good intent sometimes. These self-replicating malware is designed to retrieve some sorts of information from the infected system. Bots rarely announce their presence. These malicious programs infect networks in a way that escapes immediate notice.

Life Cycle of Virus/ Phases of Virus:

During its lifetime, a typical virus goes through the following four phases:

  1. Dormant Phase: In this phase, the malicious program Virus is idle. The virus will eventually be activated by some event, such as a date or the presence of another program of file. Not all virus have this stage.
  2. Propagation Phase: In this phase, the virus places an identical copies of itself into other programs or into certain areas on the disk. Each infected area/program in the computer system will now contain a clone of the malicious program Virus.
  3. Triggering Phase: In this phase, the virus is activated to perform the intended function. The triggering phase can be caused by a variety of system events like a specific date or exceeding the disk space to a limit.
  4. Execution Phase: In this phase, the virus perform the intended function. The performed function may be harmless or can damage files or programs of the system.

Nature of Viruses:

Viruses are designed in a way to take advantage of the details and weakness of a particular system. These malicious programs are usually specific to a particular hardware platform or a particular operating system in some cases.

Hope the nature of these malicious programs is clear up to this point.

Types of Virus:

There are numerous types of viruses but I am sharing the most significant types of Virus here. With the enormous growth of technology and available data, the count of virus types is growing. New viruses are being developed and used. So, here is the list of the most common types of viruses:

Types of Virus
  1. Memory-Resident Virus: It lodges in main memory as part of the resident system program. From that point on, the virus infects every program that executes.
  2. Stealth Virus: This malicious program/malware is explicitly designed to hide itself from any antivirus software. The purpose of the stealth virus is to defeat the virus detection/scan process. To achieve this, the signature of the virus with vary with each replication. The virus may insert superfluous instructions or can also change the order of the independent instruction inside a program.
  3. Parasitic Virus: This is the most common form of virus. A parasitic virus attaches itself to the executable files and replicates. Thus this virus infects other executable files when the infected executable file is executed.
  4. Boot Sector Virus: This virus infects the boot record or the master boot record and thus can prove to be very harmful for the system. Infecting the master boot record, this malicious program spreads when the system is booted with the disk containing the concerned virus.
  5. Polymorphic Virus: This virus mutates itself with every infection, thereby making the detection of the virus impossible.
  6. Metamorphic Virus: This is similar to polymorphic virus, with one difference that it rewrites itself completely with every infection. Hence, these virus change the detection very difficult. The metamorphic virus may change their behavior as well as appearance.

Phew… finally I was able to frame all the useful information related to malicious program – Network Security section in this post. Please comment below for any feedback or suggestions. For theon this section please read my next post here.

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