Top 10 Commonly Known Malware: A Simple Guide to Viruses, Trojans, Ransomware, and More

Malware is a scary word for anyone who uses the internet, but what does it really mean? With so many terms like virus, Trojan, and ransomware thrown around, it can feel overwhelming to understand them all especially for someone who is not geeky. But our work here at ConceptDive is to simplify things.

This article will walk you through the top 10 common types of malware, what they do, and how you can stay safe from them. By the end, you’ll feel more confident and informed, even if you’re not a tech expert.

What Is Malware?

Malware is a short form for malicious software. Any software designed to harm or exploit devices, networks, or users in any way are termed under malicious software. It sneaks into your system, often disguised as something harmless, and causes damage ranging from stealing personal data to locking you out of your files and folders.

Why Is Understanding Malware Important?

Cybercriminals are constantly evolving their tactics and in 2025 it is expected to be even more growing, affecting millions of devices. Knowing the basics can help you avoid common traps and protect your digital life online. It also helps you understand the differences and can take correct measures as per your needs.

The Top 10 Types of Malware Explained

1. Viruses

A virus is the OG of malware. It attaches itself to legitimate files or programs and spreads when you execute the infected file. Once it is active on your system, it can delete files, corrupt data, or slow down your computer. It is the most common types of malware you can even heard of.

Examples

1. ILOVEYOU Virus (2000) spread via email with the subject line “ILOVEYOU,” enticing victims to open it. Once activated, it overwrote files and propagated by sending itself to all contacts in the victim’s address book. This virus caused an estimated $10 billion in damages globally, leveraging human curiosity and trust in personal emails for its rapid spread
2. Mydoom Virus (2004) was one of the fastest-spreading email worms, causing widespread disruption by launching massive denial-of-service (DDoS) attacks on major websites and email servers. Its effectiveness lay in its rapid replication and targeting of widely used email systems.
3. CryptoLocker Virus (2013) spread through malicious email attachments, encrypting victims’ files and demanding a ransom for decryption. Its impact was significant due to its use of strong encryption, making it nearly impossible to recover files without paying the ransom.

5 ways to stay safe from Viruses?

1. Use Antivirus Software – Install a trusted antivirus program and keep it updated to detect and remove viruses. Run regular scans to catch potential threats early.
2. Avoid Suspicious Emails – Don’t open emails from unknown senders or download unexpected attachments. Watch for red flags like strange email addresses or urgent language.
3. Keep Software Updated – Always update your operating system, apps, and browser to patch security holes. Enable automatic updates for convenience.
4. Download Only from Trusted Sources – Avoid downloading software or files from shady websites. Stick to official app stores or reputable sites.
5. Be Careful with Links – Don’t click on links in random emails, texts, or pop-ups. Verify URLs before entering sensitive information.

2. Trojans

Named after the Trojan Horse from Greek mythology, Trojans disguise themselves as useful software but as soon as you install it, they allow hackers to access your device or steal data. While Viruses starts replicating and spreading across the system and destroy data but cannot pass the data back to originator. On the other hand Trojans are designed to gets access of the device and pass on the data back to originator.

Examples

• Zeus Trojan (2007) was a notorious banking Trojan that infected millions of devices. It stole sensitive data like online banking credentials by recording keystrokes and redirecting users to fake banking sites. Its impact was severe, targeting financial institutions worldwide and causing billions of dollars in losses.
• Emotet Trojan (2014) began as a banking Trojan but evolved into a powerful malware delivery tool. It spread through malicious email attachments, enabling other malware to enter infected systems. Its modular design made it versatile and one of the most damaging cyber threats.
• Remote Access Trojan (RAT) Blackshades (2010s) allowed attackers to control infected devices remotely. Hackers used it to spy on victims, steal data, and activate webcams without consent. Its widespread misuse led to global law enforcement crackdowns.

5 ways to stay safe from Trojans?

1. Use Antivirus Software – Install a trusted antivirus program and keep it updated to detect and remove viruses. Run regular scans to catch potential threats early.
2. Avoid Suspicious Emails and Attachments – Don’t open emails from unknown senders or download unexpected attachments. Watch for red flags like strange email addresses or urgent language.
3. Download Only from Official Sources – Download software only from Official sources, unofficial sources could have mod software that could be a potential be threat to system.
4. Enable Firewalls – Firewalls add a protective layer to your device, blocking unauthorized access. They can prevent Trojans from sending data to attackers.
5. Be Cautious with Links and Pop-Ups – Avoid clicking on random links, especially in emails, ads, or pop-ups. These often disguise Trojans as legitimate downloads or fixes.

3. Ransomware

Ransomware is a type of malware that locks you out of your files or device by encrypting them and demands a ransom payment to restore access. Unlike Trojans or viruses, ransomware doesn’t just steal or destroy data it holds it hostage. Victims are often left with little choice but to pay the ransom, as decryption without the attacker’s key is usually impossible.

Examples

• CryptoLocker (2013) was one of the first widely known ransomware attacks. It spread through email attachments and encrypted victims’ files, demanding payment in Bitcoin for decryption. Its strong encryption made recovery nearly impossible without paying.
• WannaCry (2017) was a global ransomware attack that exploited a vulnerability in Windows systems. It infected over 200,000 computers in 150 countries, locking users out of their files. The attack paralyzed hospitals, businesses, and governments, demanding payments in cryptocurrency.
• Ryuk (2018) targeted large organizations, including hospitals and businesses. Ryuk encrypted crucial files and demanded extremely high ransoms. It was particularly damaging because it disrupted critical operations in its targets.

5 ways to stay safe from Ransomware?

• Use Antivirus and Anti-Ransomware Software – Install reliable security software to detect ransomware before it encrypts your files. Keep it updated to stay protected from evolving threats.
• Back Up Your Data Regularly – Save copies of your important files on an external drive or cloud storage. This ensures you can recover your data without paying a ransom.
• Avoid Clicking on Unknown Links – Ransomware often spreads through phishing emails. Avoid clicking on suspicious links or downloading unexpected attachments.
• Keep Your System Updated – Regularly update your operating system and applications to patch vulnerabilities that ransomware might exploit.
• Disable Macros in Documents – Many ransomware attacks use macros in Office documents to execute malicious code. Disable macros unless absolutely necessary.

4. Spyware

Spyware is a sneaky type of malware that secretly collects information from your device without your knowledge. It tracks your online activities, records sensitive information like passwords, credit card numbers, or browsing habits, and sends it back to the attacker. Unlike viruses or ransomware, spyware is designed to operate silently in the background, making it hard to detect.

Examples

• CoolWebSearch (2003) was a notorious spyware program that hijacked web browsers, redirected users to malicious websites, and collected browsing data. It was difficult to remove and widely distributed through freeware.
• FinFisher (2010s) is an advanced spyware tool often used by governments to monitor individuals. It can record calls, track messages, and even access cameras, targeting activists and journalists in many cases.
• Pegasus (2016) is a sophisticated spyware developed by the NSO Group. It infects mobile devices and steals data, including messages, calls, and location. It’s often used for high-profile surveillance, making it a powerful but controversial tool.

5 ways to stay safe from Spyware?

• Install Anti-Spyware Software – Use a trusted anti-spyware tool to detect and remove spyware. Regularly update it to stay protected from new threats.
• Be Careful with Free Software – Avoid downloading freeware or pirated software from unverified sources, as these often come bundled with spyware.
• Keep Your System and Apps Updated – Regular updates fix vulnerabilities that spyware could exploit. Enable automatic updates for convenience.
• Use Strong, Unique Passwords – Strong passwords make it harder for spyware to access your accounts. Use a password manager to keep track of them.
• Review App Permissions – Check what permissions apps are asking for. Avoid apps that demand excessive access, like location or contacts, without a clear reason.

5. Adware

Adware is a type of malware that bombards you with unwanted advertisements. While it might seem harmless, adware can be incredibly annoying and intrusive. It can slow down your device, track your online activities, and redirect you to suspicious websites. In some cases, adware may install additional malware without your consent.

Examples

• Gator (2000s) was an early form of adware that displayed pop-up ads based on user behavior. It collected browsing habits and sold the data to advertisers, compromising user privacy.
• Fireball (2017) was an aggressive adware program that hijacked browsers and turned them into ad-clicking machines. It affected millions of computers globally and significantly slowed down browsing performance.
• DeskAd (2010s) was a popular adware program that came bundled with free software. It flooded devices with ads, often making them unusable, and sometimes acted as a gateway for other malware.

5 ways to stay safe from Adware?

• Install a Reliable Ad-Blocker – Use trusted ad-blocking extensions or apps to prevent intrusive ads from loading while you browse.
• Avoid Clicking on Shady Ads – Don’t click on pop-ups or banner ads, especially ones offering too-good-to-be-true deals or prizes.
• Download Software Only from Official Sources – Avoid freeware or pirated software, as it often comes bundled with adware. Stick to official websites and app stores.
• Pay Attention During Software Installation – Always choose custom installation and uncheck any additional offers or tools that you didn’t request.
• Keep Your Browser and Extensions Updated – Regularly update your browser and remove any suspicious extensions to protect against adware attacks.

6. Worms

Worms are a type of self-replicating malware designed to spread across networks without needing user interaction. Unlike viruses, worms don’t require a host file to attach to—they exploit security vulnerabilities to spread independently. They consume bandwidth, slow down networks, and can deliver additional malicious payloads.

Examples

• Morris Worm (1988) was one of the first worms to spread widely across the internet. It caused significant network slowdowns by replicating aggressively, highlighting the risks of poor cybersecurity practices.
• ILOVEYOU Worm (2000) spread through email with the subject “ILOVEYOU,” tricking users into opening the infected file. It replicated rapidly, overwriting files and causing an estimated $10 billion in damages globally.
• Conficker Worm (2008) targeted Windows systems, exploiting network vulnerabilities. It created botnets, disabled security features, and spread to millions of devices, making it one of the most widespread worms in history.

5 Ways to Stay Safe from Worms?

• Keep Your System Updated – Regularly update your operating system and software to fix vulnerabilities that worms might exploit.
• Use a Firewall – Firewalls block unauthorized access to your network, preventing worms from spreading across devices.
• Be Careful with USB Drives – Worms often spread through infected USB drives. Always scan external devices before using them.
• Avoid Clicking on Suspicious Links – Worms can spread via email links or malicious websites. Verify links before clicking, especially in emails from unknown senders.
• Install Antivirus Software – Use a trusted antivirus program to detect and remove worms before they can spread on your system. Keep it updated to stay protected.

7. Rootkits

Rootkits are a dangerous type of malware designed to gain unauthorized access to a system and hide their presence. They allow attackers to control devices remotely, steal data, or install additional malware without detection. Rootkits operate at a deep system level, making them extremely hard to detect or remove using standard security tools.

Examples

• Sony BMG Rootkit (2005) was a controversial rootkit installed on millions of computers through music CDs. It aimed to prevent piracy but created security vulnerabilities that hackers exploited.
• ZeroAccess Rootkit (2011) targeted Windows systems, creating a botnet for distributing other malware and enabling click fraud. It infected over 2 million devices, making it a highly persistent threat.
• Necurs Rootkit (2012) acted as a delivery tool for spam campaigns and ransomware. Its stealthy design helped it evade detection while spreading harmful payloads to millions of devices worldwide.

5 Ways to Stay Safe from Rootkits

• Enable System Updates – Regular updates patch security vulnerabilities that rootkits often exploit. Keep your operating system and software up to date.
• Use a Trusted Rootkit Scanner – Employ specialized rootkit detection tools in addition to standard antivirus software to uncover hidden threats.
• Avoid Installing Unverified Software – Only download software from official or reputable sources to reduce the risk of inadvertently installing rootkits.
• Limit Admin Access – Use a standard user account for everyday activities. Limiting admin privileges prevents rootkits from gaining full control over your system.
• Monitor Unusual System Behavior – Be alert to signs like slow performance, unexpected pop-ups, or programs running without your knowledge, which might indicate a rootkit infection.

8. Keyloggers

Keyloggers are a type of spyware that records everything you type on your keyboard. They are primarily used by attackers to steal sensitive information, such as passwords, credit card numbers, and private messages. Keyloggers can be hardware devices or software programs, and they often operate silently, making them hard to detect.

Examples

• Zeus Keylogger (2007) was a component of the infamous Zeus Trojan, designed to capture banking credentials. It was widely used in cybercrimes to steal billions of dollars from financial institutions.
• Ardamax Keylogger (2009) became popular among amateur hackers due to its easy-to-use interface. It captured keystrokes and screen activity, often used for unauthorized monitoring of personal devices.
• Revealer Keylogger (2010s) is a commonly used software keylogger that records keystrokes and sends the data to attackers. It has been misused in phishing scams and corporate espionage cases.

5 Ways to Stay Safe from Keyloggers

• Use Two-Factor Authentication (2FA) – Even if a keylogger steals your password, 2FA adds an extra layer of security that makes unauthorized access much harder.
• Install Antivirus Software – A reliable antivirus program can detect and remove keyloggers before they can record your keystrokes. Keep it updated regularly.
• Avoid Downloading Suspicious Files – Keyloggers often come bundled with freeware or malicious email attachments. Download only from trusted sources and verify file legitimacy.
• Use On-Screen Keyboards for Sensitive Data – For critical tasks like online banking, use an on-screen keyboard to bypass physical keystroke recording.
• Monitor System Behavior – Watch for signs like slow performance, unusual pop-ups, or unauthorized programs running, which could indicate a keylogger infection.

9. Botnets

Botnets are networks of devices infected with malware and controlled by a hacker, known as a botmaster. Each infected device, called a “bot” or “zombie,” works as part of the network to perform malicious activities, such as sending spam, launching distributed denial-of-service (DDoS) attacks, or spreading additional malware. Botnets can consist of thousands or even millions of devices, making them incredibly powerful and dangerous.

Examples

Storm Botnet (2007) infected millions of computers, turning them into spam-sending machines. It was also capable of launching DDoS attacks, causing significant disruptions online.

Mirai Botnet (2016) targeted Internet of Things (IoT) devices, like routers and smart cameras. It launched one of the largest DDoS attacks in history, taking down major websites and online services.

Emotet Botnet (2014-2021) evolved from a banking Trojan into a sophisticated botnet that spread malware and ransomware. It infected thousands of devices globally before being taken down by law enforcement.

10. Phishing and Scamware

Phishing and scamware are deceptive tactics used to trick individuals into providing sensitive information or downloading malicious software. Phishing often involves fake emails or websites that mimic legitimate ones, while scamware uses fear tactics, like fake antivirus warnings, to manipulate users into installing malware or paying for fake services.

Examples

• The PayPal Phishing Scam (2014) involved fake emails claiming suspicious activity in users’ PayPal accounts. These emails redirected victims to a fraudulent site that stole login credentials and financial information.
• Fake Microsoft Support Scam (2010s) tricked users into believing their computers were infected. Scammers posing as Microsoft technicians convinced victims to pay for unnecessary “repairs” or install malware.
• Locky Scamware (2016) spread via email attachments disguised as invoices. Once downloaded, it encrypted victims’ files and demanded a ransom, combining phishing and ransomware tactics.

5 Ways to Stay Safe from Phishing and Scamware

• Verify Sender Emails – Always double-check the sender’s email address and avoid responding to messages from unknown or suspicious sources.
• Be Wary of Urgent Requests – Scammers often use urgency to pressure you. Take time to verify claims before acting, especially when asked for sensitive information.
• Check Website URLs – Look for HTTPS and double-check URLs before entering personal details. Avoid clicking on links directly from emails.
• Use Email Filters – Enable spam filters to block phishing emails and reduce the chances of encountering scamware.
• Educate Yourself on Scams – Stay informed about common phishing techniques and share awareness with others to prevent falling victim to scams.

Hope you liked this article. Check out Tech Insignts for more such content.