Getting to Know the Most Common Computer Viruses

Computer viruses pose a dangerous threat that can lead to loss of personal data, identity theft, and even permanent damage of devices. By understanding how the most widespread virus types infiltrate systems and spread, you will be better equipped to secure your devices.

This guide will arm you with knowledge on the 10 virus varieties security experts encounter most. I‘ll overview how they work, real world examples, the specific harm they cause, and most vitally – precautions to lock them out of your digital life entirely.

What Exactly Are Computer Viruses?

Before surveying various virus species in the wild, let‘s cover some computer virus basics…

Computer viruses are malicious programs that attach themselves to legitimate system files or software. They circulate by self-replicating code from one system to another rather than spreading independently as a stand-alone piece of software. Once nestled into a target system, they trigger unwelcome and often destructive actions – from mild irritations like random popups to catastrophic events like permanently wiped hard drives.

Viruses spread through various vectors:

• Email attachments disguising dangerous file types as useful documents
• External storage devices like USB sticks unwittingly carrying infections
• Intentional downloads bundled with legit software, media files and documents

Once resident, viruses range vastly in impact – from annoying ad injections through to complete identity fraud after stealing banking credentials. Let’s explore the most widespread varieties.

Top 10 Viruses Burrowing Into Systems

Cybersecurity analysts universally flag these 10 as the major virus threats seeing widespread, indiscriminate distribution today:

Now let‘s unpack how these viruses infiltrate systems, the harm they inflict, and critically – precautions you must take.

1. Trojan Horse Viruses

Infection Vectors: Fake downloads for desired things i.e. games, media files, adult content.

Damage Potential: Full system monitoring, compromise and control by attackers.

Named after the legendary wooden horse that stealthily infiltrated the city of Troy, Trojan horse viruses disguise malware as useful software to tempt victims into installing them. They essentially open your computer or device to complete attacker oversight once active.

Common sources of Trojan viruses include:

• Fake anti-virus software promising to clean non-existent infections
• Video codec files claiming necessity to play a video
• Desired downloads like games, tools, adult content masking malware

Real World Example: 10 million Android users installed virus ridden apps from the official Google Play Store camouflaged as photography tools and games.

Once installed, Trojan horses can unleash:

• Complete data monitoring via logging keystrokes and screenshots
• Downloading additional malware payloads
• Cryptocurrency mining using your device‘s resources
• Financial fraud by stealing bank credentials and credit cards

How to Prevent Infection:

✅ Verify source credibility before downloading anything
✅ Use reputable antivirus suites with behavioral analysis
✅ Check app permissions carefully before installing

2. Resident Viruses

Infection Vectors: Mass spam campaigns, shared infected external drives

Damage Potential: System instability, data destruction, credential theft

Resident viruses embed themselves stealthily into the memory of systems, allowing constant harmful executions without victim detection. They spread by infecting legitimate programs, activating when those trusted applications run.

Once permanently lodged in memory, resident viruses can:

• Piggyback into other files to spread further
• Secretly sniff out sensitive credentials and data before transmitting it externally
• Download additional threats like spyware and ransomware
• Corrupt vital system processes, slowing or crashing computers

Real World Example: The ZeroAccess botnet infected 2 million systems through resident virus payloads, forming a vast network mining cryptocurrency illicitly.

How to Prevent Infection:

✅ Never open email attachments without verifying senders
✅ Use write-protection on vulnerable boot processes
✅ Install advanced endpoint protection platforms

3. Multipartite/Hybrid Viruses

Infection Vectors: Multiple routes including files, boot sectors and networks

Damage Potential: Entire system and network outages, widespread data corruption

Multipartite or hybrid viruses mix propagation techniques, evolving as they spread for maximum efficiency at infecting new targets rapidly.

Their multifaceted infection strategies encompass:

• Infecting data files, activating when opened
• Overwriting boot sectors to disable startup processes
• Utilizing file sharing vulnerabilities to spread across networks

Once entrenched, threats include:

• Formatting hard drives, destroying data
• Installing remote access backdoors
• Spreading quickly through connected networks
• Crashing vital processes

Real World Example: The BlackEnergy hybrid virus caused widespread blackouts across Ukraine by infecting critical national infrastructure systems through phishing emails.

How to Prevent Infection:

✅ Disable macros in Office files from unverified sources
✅ Scan shared network directories with updated antivirus software
✅ Make firmware and critical code read-only where possible

4. Browser Hijacker Viruses

Infection Vector: Deceived downloads masquerading as useful browser extensions

Damage Potential: Identity fraud through manipulated browsing activity, stolen credentials

Browser hijacker viruses covertly modify browser settings to force redirections, inject unwanted advertising and track user behavior illicitly. They mainly spread through deceived downloads peddled as browser extensions, tools and plugins.

Once installed, browser hijackers unleash various breeding grounds for fraud:

• Redirecting searches to promoted sites
• Tracking browsing habits to sell data
• Making browsers part of botnets without the user realizing
• Injecting invoices for fake services

Real World Example: A major browser hijacker operation drove traffic through affiliate links earning $4.5 million in fees before authorities disabled it.

How to Prevent Infection:

✅ Only install reputable browser extensions from official stores
✅ Scan devices routinely for malware
✅ Monitor browser settings for unauthorized changes

5. Overwrite Viruses

Infection Vector: Shared infected drives and removable media

Damage Potential: Permanent destruction of files beyond recovery

As the name suggests, overwrite viruses completely replace precious files and documents on systems and external devices with their own malicious code – destroying the original document beyond repair.

They often target common executable file types like .EXE and .DOC when spreading through removable drives and network shares. When infected files activate instead of the intended host program or document, overwrite viruses launch.

Beyond permanent file destruction, overwrite viruses can:

• Install spyware capturing activity on infected devices
• Transmit stolen data from corrupted files and documents
• Disable and delete security tools to maintain access

Real World Example: The Chernobyl virus overwrote critical system files eventually rendering thousands PCs completely unusable.

How to Prevent Infection:

✅ Maintain backups of precious data
✅ Scan drives and files before opening
✅ Notice file size discrepancies indicating overwriting

6. Network Viruses

Infection Vector: Exploits spreading through networked connections

Damage Potential: Entire network outages, corrupted shared resources

Unlike viruses spreading through physical media and files, network viruses exploit security weaknesses in networking platforms and operating systems to spread remotely from one infected endpoint to peer systems across shared local network connections.

Once penetrating one unsecured point like a single computer on a business network, network viruses can:

• Scan neighboring systems for vulnerabilities to penetrate
• Spread quickly across organization networks
• Corrupt shared network resources like servers and storage drives
• Install backdoors for persistent remote access after discovery

Real World Example: The SQL Slammer network virus caused a global internet slowdown by rapidly flooding tens of thousands of vulnerable servers with malicious traffic.

How to Prevent Infection:

✅ Patch and update networking devices and servers
✅ Harden network configurations securely
✅ Isolate and scan suspected infected systems immediately

7. Polymorphic Viruses

Infection Vector: Targeted malware attacks bundled with everyday software installs

Damage Potential: Undetected rootkit deployments, ransomware, data destruction

Polymorphic viruses dynamically modify their code as they spread to avoid static detection signatures used by antivirus tools. They also often compress themselves for rapid distribution through email and network channels.

Common infection points include:

• Weaponized downloads masquerading as document templates, media files and codecs
• Network exploits like Waterhole attacks

To camouflage further, polymorphic viruses commonly:

• Encrypt functional parts of their code
• Compress themselves into small executable payloads
• Self-modify repeatedly

Morphing allows them to infiltrate networks avoiding security inspection. Once embedded, common objectives include:

• Deploying stealthy rootkits for remote access
• Extracting and exfiltrating sensitive data
• Locking files for ransom
• Sabotaging databases

Real World Example: The Satan bug virus mutated rapidly to attack UNIX networks undetected through compromised scripts, infecting subsequently Apple Mac devices.

How to Prevent Infection:

✅ Scan questionable email attachments
✅ Update antivirus software frequently
✅ Monitor systems for unusual behavior or crashes

8. Macro Viruses

Infection Vector: Shared infected documents and media

Damage Potential: Widespread software corruption, instability and data loss

Macro viruses target popular office productivity suite documents like Word, Excel and PowerPoint files specifically. They embed malicious scripts into the legitimate programmable macro functions relied on by corporations globally.

Macro viruses tend to spread unsuspectingly through:

• Infected files on shared drives
• External media like USB sticks
• Email attachments often posing as invoices

Once opened by victims, they trigger the malicious macros, initiating things like:

• Self-replication by infecting further stable documents and templates
• Corrupting data integrity prompting recovery headaches
• Spawning additional malware downloads

Microsoft disables macros by default these days as an infection vector hedge. But users often override this protection not realizing it re-enables these dangers.

Real World Example: The infamous Melissa macro virus caused email servers and networks to crash as message volume soared with its rapid self-spreading.

How to Prevent Infection:

✅ Never override Microsoft Office macro security restrictions
✅ Scan documents from external sources before opening
✅ Monitor software stability for any corruption

9. Boot Sector Viruses

Infection Vector: Shared media like USB sticks, CDs and DVDs

Damage Potential: Complete system failure, hardware destruction

Boot sector viruses embed deep into the boot sectors of media like hard drives and USB sticks. Boot sectors contain code vital to initializing operating system startup processes.

With such low-level access, boot sector viruses can execute before the OS loads, circumventing detection. They spread primarily through:

• Infected external USB drives, discs and DVDs
• Exploiting network weaknesses to overwrite master boot records

Once embedded, boot sector viruses can:

• Override normal boot sequences
• Load malicious processes before users login
• Permanently destroy boot configuration code
• Prevent hardware like hard drives from being read

Real World Example: The Michelangelo virus triggered lethal boot sector corruption every March 6th destroying critical commercial systems yearly.

How to Prevent Infection:

✅ Set boot sectors and firmware as read only where possible
✅ Maintain backups of precious data
✅ Disable autorun capabilities on external media

10. Web Scripting Viruses

Infection Vector: Vulnerable web apps and uploaded files

Damage Potential: Server outages, client device infections

Web scripting viruses specifically target web servers and hosted sites by embedding malicious code into the normal HTML, JavaScript, PHP and ASP files rendering pages to visitors.

They mainly leverage two common weaknesses to infiltrate sites:

• Security vulnerabilities in outdated content management systems like WordPress and vBulletin
• Uploaded infected files from compromised administrator accounts

Real World Example: Over 1 million legitimate websites were compromised to deliver steganographically concealed malware to visitors through malicious advertising injections.

Once embedded in vulnerable pages, web scripting viruses trigger automatically when visitors browse infected sites. Payloads frequently involve:

• Spreading malware further through browser security holes
• Installing keyloggers tracking site visit behavior
• Leveraging visitor computers to spread spam
• Forcing unwanted advertising clicks

How to Prevent Infection:

Site operators should…
✅ Patch site software vulnerabilities immediately
✅ Vet uploaded script files strictly
✅ Limit admin access to legitimate users

Site visitors should…
✅ Avoid suspicious looking small niche sites
✅ Scan devices if installed software behaves oddly
✅ Use script and ad blockers

Securing Your Digital Life Against Viruses

While robust endpoint protection software goes a long way, users play a pivotal role in preventing infection too. Here are key precautions everyone should action to avoid these digital diseases:

Keep Software Fully Updated

Hackers notoriously leverage outdated applications containing fixed security holes. Regularly patching and upgrading your operating system, apps, browser and plugins closes vulnerabilities viruses utilize. Enable auto updates wherever possible.

Practice the 3-2-1 Backup Methodology

Maintaining current backups of precious data across multiple media gives you resilience should viruses impact files and systems. Retain 3 copies, on 2 different formats with 1 off-site or cloud version.

Test restores regularly to verify backups.

Limit User Account Privileges

Reducing application and system rights that standard user accounts have constrains malware should it penetrate defenses. Run as a standard user for everyday browsing and app usage for added safety.

Closely Inspect Downloads and Email Attachments

Scrutinize all files before opening – especially from less trusted sources. Scan attachments, media files, documents and discs for malware signatures.

Verify email senders are legitimate through contact before enabling any scripts or macros.

Stick to Reputable Sites and Apps

Malware frequently conceals within apps and media from unofficial outlets. source software and extensions only from official platform vendors like Google and Apple.

Similarly, restrict browsing to mainstream websites with full security protocols when possible.

Install Commercial-Grade Security

Robust cybersecurity tools like Trend Micro’s aptly named ‘Apex One’ stop the latest sophisticated threats that bypass consumer protections.

Utilize layered next-gen endpoint suites across your network for fully up to date detection.

Staying vigilant requires ongoing security posturing through fundamental precautions like patching rigorously, vetting access and hardening configurations. But it also relies on wise judgment when interfacing with downloads and communication from cyberspace.

Let‘s Stamp Out Viruses For Good!

We‘ve covered a lot of ground here. Now you know your macro viruses from your overwrite critters and everything in between!

The key takeaway is that while virus creators constantly evolve infections, smart precautions confine the vast majority before harm. By yeilding some best practice security habits, you can navgate cyberspace safely and avert the chaos viruses endeavour to unleash.

Here‘s to a malware-free future ahead! Please reach out if you have any other virus concerns I can address. I‘m always happy to help individuals and organizations bolster their protection.