Skip to content

7 Types of Malware | Signs of Malware Infection & Preventive Measures

The word malware is a combination of the words malicious and software. In layman terms, malware is any software program whose sole purpose is to cause harm to computer systems. Hackers frequently use these programs for stealing data or causing disruption. Additionally, cybersecurity researchers may also experiment with various types of malware for penetration testing methods.

It is extremely important for individual users as well as companies to use anti-virus software or firewalls to protect against the mushrooming presence of malware on the internet.

The following are some of the most common types of malware that infect computers worldwide –

  1. Virus
  2. Worms
  3. Bot
  4. Ransomware
  5. Rootkit
  6. Spyware
  7. Trojans


A computer virus is one of the most common types of malware on the internet. It is a piece of malicious code that is capable of copying itself and spreading to other files and folders. Viruses can attach themselves to legitimate executable programs and launch when the program is executed.

Viruses can perform a wide array of harmful functions – modify or corrupt files, copy data, disrupt software functions, create botnets, etc. While commercially available anti-virus software can help disinfect systems, it is quite difficult to remove a virus completely. That is because of its self-replicating function. Most anti-viruses can at most, quarantine corrupt files for deletion, to prevent the virus from spreading.


Similar to viruses, worms are also among the most common types of malware. However, unlike a virus, a worm does not need any user action to spread across the system. Worms are self-replicating and infect computers through vulnerabilities in operating systems and spread to others through a network. 

While most worms cannot cause any significant damage, they can consume a lot of bandwidth and overload servers. However, a small number of worms have been known to make changes to existing files. Hackers can use worms and deliver payloads into target computers to steal data, corrupt files, disrupt system functions, etc. A payload is a malicious program for carrying out cyberattacks.

Any reputed anti-virus software is usually good enough to prevent and remove worms in computers.


A bot or internet bot, is an application that performs certain automatic functions.  Bots enable programmers to carry out important, repetitive tasks that are too fast for human beings. While bots are generally harmless and used only for commercial purposes, malicious bots are intended to cause harm. 

Hackers engineer bots to infect computers and enable themselves to perform large scale distributed denial of service attacks (DDOS). This is possible by programming bots to infect several computers and form a botnet to flood a server with more requests than it can handle. A botnet is a network of many interconnected devices that are running bots.

Additionally, cybercriminals also use bots for causing inconvenience like spamming and repetitively showing certain advertisements. Web servers requiring login credentials usually have preventive measures like CAPTCHA for defending against DOS (Denial of Service) or DDOS attacks.


As the name indicates, ransomware is a malware that completely locks a computing system until users pay a ransom. Ransomware has been frequently used in cyberattacks in the last few years. When this malware infects a computer, the user is unable to use it and a message on the desktop demands payment. 

Ransomware spreads like a worm across a network and can cripple an entire organization within a few hours. This type of malware is very serious and difficult to disinfect. The Wannacry ransomware attack was one of the worst cyberattacks in history. Originating from Asia, Wannacry spread to nearly a quarter of a million computers in more than 150 countries in just a few days. Infected computers had a message on their screens demanding payment in bitcoins.

In addition to individual users, organizations must use leading anti-virus software and perform regular updates to defend against ransomware attacks.


Rootkits are one of the most damaging types of malware. They are very difficult to detect & remove and provide the perpetrators almost complete access to the target computer. A hacker who installs a rootkit into a computer can access & steal data, delete or corrupt files, spy on all system activities, modify programs, etc. Since rootkits remain constantly hidden and avoid detection, most commercially available anti-virus software is ineffective against them.

Rootkits can remain hidden for months, even years before users realize that something might be wrong with their systems. As a result, the only effective way to remove rootkits is through exhaustive manual analysis of system functions and behavior. A large number of cyberattacks around the world have been carried out successfully through the use of specially designed rootkits.


Spyware is malicious software that collects information on user activity and sends it to others without the users’ knowledge. It may do so through monitoring usage, logging keystrokes, gathering data on certain activities, etc. In addition to regular operating system updates, any commonly available anti-virus is enough to prevent spyware infection.

In addition to spyware being maliciously used by cybercriminals, similar, legitimate software is common among companies and government agencies to track employee activities and prevent suspicious behavior.  


A Trojan horse or Trojan is a malware that is specifically designed to cause harm to computer systems or networks. The purpose of a Trojan could be to steal data, erase or modify files, alter system configuration, log keystrokes, etc. It’s name derives from the Trojan horse used by Greek soldiers in Homer’s epic, The Iliad.

Trojans appear as common, harmless attachments or downloadable files that sometimes may not be detectable by anti-viruses and firewalls. However, upon downloading, Trojans can cause extensive damage to computers and may even enable hackers to control them remotely. They begin execution only after unsuspecting users open them.

As a result, Trojans are a weapon of choice for black hat hackers around the world. Cybercriminals send them through email attachments so that they can bypass a company’s firewall. Moreover, various social engineering techniques also enable malicious individuals to upload Trojans into their victims’ computers. Therefore, it is important that users don’t allow strangers to use their computers or smartphones without supervision.

Common Signs of Malware Infection

While different types of malware have varying effects, most of them produce similar symptoms. Users must immediately begin scanning their computers if any of the following signs persist –  

  1. Slowing down of systems
  2. Continual reduction in browsing speeds in spite of hi-speed internet connection 
  3. Specific programs or applications slowing down frequently
  4. Recurrent freezing or crashing
  5. Modification of files
  6. Change in system settings
  7. Missing files
  8. Random appearance of new files
  9. Increase in heat resulting from rising in CPU usage
  10. Applications shutting down or exhibiting frequent changes in configurations

Preventive Measures

Every user must take some common precautions to prevent malware from infecting his/her computer – 

  1. Users must use reliable, authentic anti-virus software and conduct periodic scans
  2. Avoid using pirated software and operating systems. They often harbour several exploitable vulnerabilities
  3. Keep software and operating systems up-to-date
  4. Do not download anything from unknown or suspicious websites
  5. Do not connect pen drives or insert disks from unknown sources
  6. Users must never open or download attachments in emails from unknown senders


Texial, is a non-profit organization established under Section 8 of the Companies Act. We offer a wide range of cybersecurity and forensic services to private organizations as well as government agencies. 

As part of our unwavering commitment to making the internet safer for everybody, we organize awareness campaigns and conduct workshops in educational institutions and companies. Additionally, Texial Lab also offers courses in digital security and forensics to individuals and law enforcement agencies to combat cybercrime.

Join Texial Lab to launch an exciting career in cybersecurity!

Enroll in a Ethical Hacking Boot Camp and earn one of the industry’s most respected certifications — guaranteed.

-Live online ethical hacking instruction
– Exam Pass Guarantee
– CEH exam voucher

Related courses

  • Texial Certified Hacker
  • Certified Ethical Hacker
  • SOC Certifcation

Defend your business against
the Latest Cyber Threats

share it