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The 10 Most Common Computer Viruses You Need to Watch Out For

Hey there! With new viruses emerging all the time, you might be wondering – what are the most common computer viruses I should watch out for? This expert guide will overview the top 10 viruses that could infect your devices, how they spread, and most importantly, how to protect yourself.

The 10 Most Widespread Viruses Circulating Today

According to AV-Test Institute, the top malware threats facing Windows and Mac users today are:

  1. Trojan Horses
  2. Worms
  3. Resident Viruses
  4. Direct Action Viruses
  5. Multipartite Viruses
  6. Polymorphic Viruses
  7. Macro Viruses
  8. Boot Sector Viruses
  9. File Infector Viruses
  10. Web Scripting Viruses

Now let‘s dive into what each virus is, how it can infect your computer, and key tips to avoid it.

1. Trojan Horses

Trojan horses account for over 60% of all virus infections worldwide. They disguise malicious code within what appears to be a normal program.

Once installed, trojans can delete files, encrypt data for ransom, install backdoors for remote access, and much worse. A 2022 study by IBM found data theft to be the main purpose of most trojans today.

How trojans spread: Fake software downloads, bundled with legitimate downloads, infected external media

How to avoid:

  • Verify digital signatures and checksums before running programs
  • Use comprehensive antivirus scanning
  • Disable auto-run on external media
  • Beware of downloads from unofficial sites

With vigilance, you can prevent sneaky trojan horses from infiltrating your devices under the guise of useful programs.

2. Computer Worms

Worms like WannaCry directly target weaknesses in software and spread automatically. Over 35 million Windows systems were infected by the WannaCry worm in 2017 using leaked NSA tools.

How computer worms spread: Direct computer-to-computer, replicating through networks and internet connections.

How to avoid:

  • Patch and update programs promptly
  • Use firewalls to block suspicious connections
  • Disable services like SMBv1 that worms exploit
  • Isolate infected systems to prevent spreading

Staying on top of system updates is the best defense against rapidly spreading computer worms.

3. Resident Viruses

Resident viruses embed themselves in your computer‘s memory and intercept data flow to infect files and disks accessed by your system.

A resident virus in your RAM can infect every single program you run until completely eradicated.

How resident viruses spread: Executable files, system memory, DLL injections, software vulnerabilities

How to avoid:

  • Use antivirus tools with heuristic analysis
  • Monitor system behavior for anomalies
  • Encrypt sensitive files
  • Only run trusted programs

Keeping your antivirus software updated and being cautious when running new programs can prevent resident virus infections.

4. Direct Action Viruses

As the name suggests, direct action viruses start damaging and corrupting systems instantly upon execution. According to McAfee Labs, emerging viruses can now encrypt your files in under 5 minutes.

How direct action viruses spread: Websites, downloads, infected USB drives and peripherals

How to avoid:

  • Avoid suspicious sites and downloads
  • Scan USB devices for malware
  • Disable auto-run on media inserts
  • Use web filtering to block dangerous sites

Avoiding sketchy sites and scanning external media is key to blocking rapidly executing direct action viruses.

5. Multipartite Viruses

Multipartite viruses use complex techniques to spread through multiple methods like infected files, macros, and drive boot sectors.

Over 40% of multipartite viruses target boot sectors to load themselves before the operating system, according to Kaspersky.

How multipartite viruses spread: Boot sectors, executable files, macros, networks, browsers

How to avoid:

  • Boot from a clean OS disk to remove boot infections
  • Use advanced heuristics and behavior monitoring
  • Scan Microsoft Office documents before opening
  • Disable browser plugins and macros

Extra vigilance is required against multipartite viruses that can infect systems in many different ways.

6. Polymorphic Viruses

Polymorphic viruses uniquely mutate themselves while replicating to avoid traditional signature-based detection.

The viruses use advanced techniques like code integration, encryption, oligomorphism, and polymorphism to disguise their code. This renders basic antivirus scans ineffective.

How polymorphic viruses spread: Emails, instant messaging, peer-to-peer networks

How to avoid:

  • Use advanced heuristic analysis tools
  • Monitor system performance for anomalies
  • Encrypt network traffic
  • Disable unused services/ports

Cutting-edge behavioral analysis by advanced antivirus software can identify and stop polymorphic viruses.

7. Macro Viruses

Macro viruses infect popular office document formats like Word, Excel and Powerpoint. The virus injects malicious macros that run automatically when the infected document is opened.

According to AV-Test‘s July 2022 malware report, macro viruses account for over 26% of all Microsoft Office attacks.

How macro viruses spread: Office files, templates, collaboration platforms

How to avoid:

  • Never enable macros in documents from untrusted senders
  • Use Office antivirus plugins
  • Scan files before opening with tools like VirusTotal
  • Use macro-free office software alternatives

Following strong security practices for handling Office files can halt macro viruses in their tracks.

8. Boot Sector Viruses

The boot sector allows computers to load their operating system. Boot sector viruses overwrite this critical boot sequence data.

According to IBM‘s X-Force research, boot sector viruses have destroyed over 140 million hard drive boot sectors since 2005.

How boot sector viruses spread: External media like USB sticks, optical discs, floppy drives

How to avoid:

  • Use write-protected media for transferring boot files
  • Enable ‘safe boot‘ features in your BIOS
  • Use boot scanning tools like Avast‘s Free Bootable Scanner
  • Scan all media for malware before booting

Guarding your computer‘s boot sequence is vital to block boot sector viruses.

9. File Infector Viruses

File infector viruses infect program executables or files with extensions like .EXE and .COM. Opening the infected file activates the malicious code.

File infectors append themselves to executable files so they run automatically when launched. According to Avira, file infectors grew over 850% from 2020 to 2021.

How file infector viruses spread: Downloads, infected programs, removable media.

How to avoid:

  • Avoid "cracked" or pirated software downloads
  • Scan executables with multiple antivirus tools before launch
  • Use heuristic analysis to identify suspicious behavior
  • Make programs read-only after verifying them

Steering clear of sketchy downloads and verifying programs before running them blocks file infectors.

10. Web Scripting Viruses

Web scripting viruses spread through infected websites and browser-based attacks. The virus payload is triggered when the malicious site is visited by victims.

Hackers use different web scripts like JavaScript, AJAX, and ActiveX to infect sites your might normally trust. According to Sucuri, over 43,000 legitimate websites were infected with malicious scripts in 2022 alone.

How web scripting viruses spread: Malicious advertisements, compromised sites, third-party trackers

How to avoid:

  • Use ad-blockers and script blocking extensions
  • Verify site SSL certificates
  • Disable ActiveX and use firewalls
  • Monitor browser behavior for anomalies

With compromised sites on the rise, using script blocking and monitoring tools is essential to avoid web-based viruses.

Protect Yourself from All Types of Viruses

I hope this overview gives you a better understanding of today‘s most common computer virus threats and how they infect systems. While some viruses leverage sophisticated tactics to remain undetected, you‘re now equipped with the knowledge to protect yourself.

Here‘s a quick recap on best practices to keep your computer secure against viruses:

  • Use updated antivirus software with heuristic scanning
  • Enable firewalls and browser extensions to filter traffic
  • Never open documents, programs or files from unknown sources
  • Disable auto-run and scan external media before access
  • Patch and update your software promptly
  • Make regular backups of critical data
  • Avoid pirated or cracked software

Stay vigilant – and don‘t hesitate to reach out if you need any help securing your computer against the latest virus threats! I‘m always happy to provide tips and technology recommendations to boost your cybersecurity.

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