TL;DR
- Email is the most common delivery route, with 41 percent of malware arriving through an attachment or a link (SentinelOne, 2026).
- Compromised websites account for another 23 percent, and unpatched software holes for 17 percent (SentinelOne, 2026).
- Fake “your browser needs updating” popups on legitimate websites are one of the most successful traps running right now.
- Nearly every infection needs you to do something first, which is why habits protect you better than software alone.
- If a popup gives you a phone number to call, that number belongs to the scammer. Never call it.
How Does a Virus Get On Your Computer?
Almost every infection starts with a click. You open an email attachment, download a file, click a popup, or install a program that carries something extra. Email is the single biggest route, delivering 41 percent of malware through attachments and links (SentinelOne, 2026).
Computers rarely get infected on their own while sitting idle. Something has to run, and in most cases a person is the one who runs it.
That’s good news, because it means your habits matter more than which antivirus you bought.
Virus or Malware? The Difference Worth Knowing
Malware is the umbrella term for any harmful software. A virus is one specific type that copies itself by attaching to other programs.
Most of what people bring us isn’t technically a virus. It’s adware pushing popups, a trojan pretending to be a useful program, an infostealer harvesting saved passwords, or ransomware locking files for payment. Trojans alone account for a large share of what’s out there (Astra, 2026).
The label matters less than the effect. We use “virus” the way most people do throughout this article, meaning any harmful software that shouldn’t be on your machine.
The 5 Ways Malware Actually Reaches Your Computer
Research tracking real infections puts them into a small number of categories, and the ranking has stayed remarkably consistent.
| Route | Share of Infections | What It Looks Like |
|---|---|---|
| Email attachment or link | 41% | An invoice, receipt, resume, or delivery notice you weren’t expecting |
| Compromised or fake websites | 23% | Fake update prompts, malicious ads, spoofed download pages |
| Software vulnerabilities | 17% | An outdated browser, plugin, or operating system being exploited |
| Removable media | 9% | An infected USB drive plugged into your machine |
| Supply chain compromise | 7% | Legitimate software carrying malicious code after a vendor breach |
Source: SentinelOne, 2026. The percentages shift year to year, but email and web routes have led the list for a long time.
The Fake Browser Update Popup That Catches Almost Everyone
You visit a normal website, and a message appears saying your browser is out of date and needs an update to continue. It looks convincing. You click it, a file downloads, and you’ve just installed malware yourself.
This trick works because it appears on real websites that attackers have compromised, so nothing feels suspicious about where you are. One campaign using this method dominated malware detections for seven straight quarters (Center for Internet Security, 2025).
The rule that defeats it is simple. Browsers update themselves in the background and never ask you to download an update file from a website. If a webpage tells you to update your browser, close the tab. To check for real, open your browser’s own settings menu and look there.
What an Infected Computer Actually Looks Like
Infections announce themselves in fairly predictable ways. Any one of these is worth checking out.
- Your browser opens a different search engine or homepage than the one you set, and changing it back doesn’t stick.
- Popups appear outside the browser, including when no browser window is open at all.
- The fan runs constantly and the machine feels hot even when you’re not doing much, which can mean something is using your processor in the background.
- New toolbars, extensions, or programs appear that you never installed.
- Your antivirus is switched off and won’t turn back on, since disabling it is one of the first things malware tries.
A slow computer on its own usually isn’t an infection. Aging hardware causes that far more often, and our guide to SSD vs HDD covers the most common reason.
The Popup With a Phone Number Is Always a Scam
Some popups fill the whole screen, play an alarm sound, claim your computer is infected or locked, and give you a support number to call. Every part of that is fake, including the number.
Calling connects you to someone who will ask for remote access to your computer, then either install real malware, take payment for a fix nobody needed, or go after your bank details. The popup itself often does no damage at all until you make that call.
No real company puts a phone number in a security warning on your screen. If you see one, close the browser using Task Manager if the window won’t close normally, then restart. If you already gave someone remote access, disconnect from the internet and get the machine looked at.
What Actually Prevents Infections
Prevention comes down to a handful of habits, and they matter more than which security product you run.
- Install updates when they appear, since 17 percent of infections come through software holes that were already patched (SentinelOne, 2026).
- Treat unexpected attachments as suspicious even when the sender looks familiar, because compromised accounts send real-looking mail.
- Download software only from the maker’s own website rather than from a search result or download portal.
- Use Windows Defender or another reputable antivirus and leave it turned on, rather than running several security programs at once.
- Back up your files to an external drive or cloud service, which is the only thing that reliably beats ransomware.
That last one deserves emphasis. Ransomware encrypts your files and asks for payment. A current backup turns that from a disaster into an inconvenience.
Virus Removal in Sterling, VA: What to Expect at PC Mobile
PC Mobile has handled virus removal for Loudoun County customers since 2013. We clean the infection, check what it touched, and tell you which passwords need changing, because infostealers grab saved logins before anything else.
Every job comes with a 30-day warranty. If the machine turns out to be slow for reasons unrelated to malware, we’ll tell you that instead of charging for a cleanup you didn’t need.
We also handle slow computer repair and RAM upgrades. See all computer repair services.
Related reading: SSD vs HDD explained, what RAM actually does, MacBook vs Windows laptop, and what’s inside a Google Pixel screen.
Frequently Asked Questions About Computer Viruses
How does a virus get on your computer?
Most infections arrive through email attachments and links, which account for 41 percent of cases, followed by compromised websites at 23 percent (SentinelOne, 2026). Nearly all of them require you to open, click, or install something first.
Can you get a virus just from visiting a website?
It’s possible but uncommon, and it usually requires an unpatched browser or plugin. The far more common version is a website showing you a fake update prompt or download that you then click yourself.
Does antivirus software stop every virus?
No. Antivirus catches known threats well and newer ones less reliably, and malware often tries to disable it first. Updates, backups, and cautious clicking do more for your protection than any single security product.
How do I know if my computer has a virus?
Watch for browser settings that change back on their own, popups appearing outside the browser, programs you never installed, constant fan noise while idle, and antivirus that won’t stay on. A computer that’s simply slow usually has a hardware reason instead.
What should I do if a popup says my computer is infected and gives a phone number?
Don’t call it. Legitimate security warnings never include a support number. Close the browser, using Task Manager if needed, then restart the computer. If you already granted someone remote access, disconnect from the internet and have the machine checked.
Can Macs get viruses?
Yes. Macs face less malware than Windows machines but they aren’t immune, and adware and fake update prompts target macOS regularly. The same habits apply on both platforms.
Think Something’s On Your Computer? Bring It In
If your browser is behaving strangely, popups keep appearing, or you clicked something you now regret, get it looked at sooner rather than later. Infostealers work quickly, and the faster we clean it, the less there is to worry about afterward.