So What Actually Are Computer Viruses, Anyway?

You‘ve probably heard about nasty viruses like WannaCry or Mydoom in the news. Tales of infected computers, encrypted files, stolen data and million dollar damage costs make them sound like digital boogeymen. But for the average person, what are computer viruses, what makes them dangerous, and how likely are you to get infected? Read on dear friend – I‘ll be your guide to the virus underground!

Let‘s start with the basics…

Defining Computer Viruses

Computer viruses are malicious programs that infect devices and systems to cause chaos. Just like human viruses hijack cells to replicate themselves biologically, computer viruses infiltrate software programs and systems before unleashing their payloads.

Specifically, computer viruses:

Infect executable files and programs
Make copies of themselves
Spread those viral copies to additional programs/systems
Often contain damaging payloads alongside their replication code

Payloads disrupt normal functioning by deleting documents, encrypting data for ransom, stealing sensitive information, slowing performance and crashing systems entirely.

Now an important distinction – viruses are not the same as malware, which encapsulates any malicious software threat. Viruses deserve special notoriety because spreading is literally coded into their DNA!

A Brief History of Computer Viruses

Patient zero – The very first computer virus was Creeper, created by Bob Thomas way back in 1971. The experimental ARPANET malware infected DEC PDP-10 computers, copying itself remotely and displaying a friendly message to shocked admins!
The Brain – This virus kicked off the MS-DOS virus wild west in 1986. Found on floppy disks worldwide, it infected the boot sector to display a mocking poem on every 90th reboot.
Melissa – This shockingly viral macro virus snarled email systems in 1999 by mass-mailing itself to Outlook contacts upon execution. It caused over $80 million in cleanup costs!
I LOVE YOU – Ironically unleashed just before Valentine‘s Day 2000, this innocent seeming worm actually contained keylogging and mass-mailing replication functionality. It ultimately caused $15 billion in damage globally.
Code Red – Targeting a Windows server vulnerability in 2001, the Code Red worm infected over 1 million systems in just 14 hours! Its backdoor payload let remote attackers compromise servers worldwide.

Fast forward to today, and the virus golden age rages on. Patient zero Creeper seems quaint compared to the chaos caused by modern virus rockstars like WannaCry. Let‘s break down the most common computer virus VIP lists!

Categories of Computer Viruses

Viruses span a wide range of species and families under the malware genus. Let‘s cover some of the most prominent categories, from boot infectors to macro viruses:

Boot Sector Viruses

As the name implies, these target and rewrite the boot sector section on storage media like hard drives and USB sticks. When infected devices are booted, the virus loads itself into memory and proceeds to infect the boot sectors of additional connected drives. Floppy disk-era veterans like Michelangelo and Stoned fell into this bucket.

Macro Viruses

Lurking inside everyday Office documents, these infections write malicious macros that run automatically when infected files open. Spreading is a cinch via email attachments and downloads. Macro master Melissa outbreak cost enterprises over $100 million back in the 90s, while modern strains continue causing trouble.

File Infector Viruses

Instead of Office macros, these old school viruses go straight for the binary. They target and overwrite critical system files like EXEs and DLLs with infected copies. Upon execution (often via boobytrapped email downloads), the virus unpacks itself before injecting code into additional binaries. DOS-era giants Jerusalem and CIH both used classic file infection tactics.

Virus Category	Infection Target	Spread Method	Example Outbreaks
Boot Sector	Boot sector/partition	Removable drives, floppies	Michelangelo, Stoned
Macro Virus	Office documents	Email attachments	Melissa, Bablas
File Infector	System binaries	Execution of infected files	Jerusalem, CIH

And while technically not viruses based on how they spread, both worms and trojans deserve quick mentions:

Worms

Worms like Code Red and WannaCry contain aggressive self-propagation logic enabling rapid blast radius expansion. Unlike viruses, they spread automatically by exploiting software security holes – no user execution required! Worm outbreaks often start small before cascading into system-crashing enterprises disasters.

Trojans

Trojans disguise themselves as useful software, duping victims into inviting them inside. Modern trojans have graduated from simplistic "Free Calculator" apps though, now leveraging complex social engineering and custom malware toolkits. Once executed, trojans can destroy files, steal data, or fully compromise system control.

Now onto the most critical virus dimension – just how much damage can these digital parasites cause?

Destructive Effects of Viruses

Viruses run the gamut from mere annoyances to biz-ending catastrophes based on their payloads. Observed outcomes include:

Corrupted/Deleted Documents – Payloads that encrypt or systematically overwrite critical files. In ransomware attacks, restoring access requires exorbitant bitcoin payments.
System Instability – Viruses hog computing resources like CPU, memory and disk space. Performance tanks, crashes increase, reboot loops occur regularly.
Stolen User/Enterprise Data – Keylogging, screenshotting and covert data extraction tactics pilfer account credentials, emails, IP and more for extortion.
Hard Drive Destruction – Certain payloads directly target storage media by initiating rapid, repeated overwrite cycles. Say bye to mechanical drives!
Ransom Demands – File-encrypting malware is useless without the decryption keys. Victims must pay steep ransoms or watch business grind to a halt.
Zombified Systems – Backdoors allow attackers unfettered remote access to issue commands. Botnets of thousands of devices can be amassed.

Of course, quantifying damage isn‘t just a philosophical exercise:

Virus Name	Year	Estimated Damage	Details
ILOVEYOU	2000	$15 billion	This worm spread as a love letter email attachment and mailed itself to Outlook contacts before overwriting image, music and document files globally.
Mydoom	2004	$38 billion	The fastest spreading email worm ever reportedly caused $1 billion per week in lost productivity due to downtime and Web outages.
WannaCry	2017	$4 billion	Encrypted critical medical records and machinery like MRI machines in hospitals, sidelining emergency rooms worldwide.

So in summary – viruses can range from an excuse to delay work, to enterprise-enders threatening bankruptcy. Now onto the million dollar question – how does one actually get infected?

Attack Vectors: How Viruses Spread

Like highly infectious human outbreaks, computer viruses leverage any avenue they can to spread widely:

When users execute mystery email attachments or embedded web links, viruses launch before replicating and mailing themselves out to wider contact lists.
Vulnerable network shares with loose security settings allow viruses to traverse networks, infecting loosely secured machines.
Website drive-by attacks trick users into downloading malware payloads, providing fake security warnings as cover.
USB drives get compromised after being plugged into infected machines. Autorun processes kick off malware execution upon re-insertion elsewhere.

Fundamentally, any software vulnerability enabling unverified code execution ups virus infection odds substantially. And with users constantly installing new apps with 0-day flaws, fresh attack surfaces continually emerge.

So based on everything covered, what‘s the game plan for keeping viruses away from our precious data?

Protecting Yourself from Virus Mayhem

Given the ubiquity of viruses, solid defensive measures are a must:

Deploy updated antivirus software – Mainstream AV packages from Bitdefender, Norton and others detect most malware using signature databases or behavioral clues.
Patch, patch, patch – Updates eliminate exploitable software flaws used by viruses to infiltrate networks – so apply them ASAP.
Avoid suspicious downloads/attachments – Vet senders before opening files or clicking unfamiliar links in messages. Hover over hyperlinks to check real domains – fake login pages are common!
Toggle off Office macro execution rights – Macro viruses can‘t activate without these permissions, disabling key intrusion points.

Of course, with malware innovating daily, the good guys must work round the clock adapting their virus extermination toolkits…

The Virus vs. Security Arms Race

Like an eternal cold war, virus developers and cybersecurity defenders continually upgrade their arsenals in a high stakes arms race playing out across the digital realm.

Attackers have rolled out an increasingly devious array of innovations over the years:

Advanced polymorphic features to mutate viruses beyond signature detection
Stealth tactics like disabling antivirus processes or tricking detection checks
Hybridized threats combining worm self-propagation with sinister data-stealing payloads

And defenders haven‘t been sitting idle either! Security pros now wield next-gen capabilities to snuff out emerging outbreaks:

Machine learning models spot anomalies indicative of patient zero infections
Big data pipelines aggregate enterprise-wide signals to reveal attack commonalities
Honeypots and sandboxes safely detonate suspected malware samples before analyzing their inner workings

But just like the cold war, clear winners remain elusive as both sides stockpile code firepower. The saving grace is that increased awareness around virus behaviors helps internet citizens spot early warning signs before things get out of hand!

Let‘s Recap!

We‘ve covered a ton of ground in the secretive world of computer viruses. To recap:

Viruses are destructive parasites that infect host systems before replicating to others. They often have malicious payloads beyond just self-copying code.
Early experimental viruses set the stage, but modern worms and trojans have graduated to enterprise-scale attacks.
Variants span boot sector inflectors, Office macro viruses, file overwrite viruses and more – but all aim to spread quickly.
While originally spread by floppy disks, emails, websites and unpatched software holes now enable flash distribution at scale.
Encrypted documents, stability issues, data theft and ransom demands represent growing real-world consequences.
With billions in potential damages, users must minimize attack surfaces by patching diligently, vetting links/attachments and running robust antivirus tools.

And with that, friend – hopefully you‘ve got some handy new virus insights to apply for protecting your precious data! Stay safe out there as malware madness continues crescendoing across the digital landscape.