Pop-up ads
Running into pop-up ads while surfing the Web used to be par for the course. Thanks to pop-up blocking now standard in modern browsers, these annoyances aren't common.
Still seeing pop-ups online from multiple sites? It could be a badly-configured browser.
Seeing pop-ups when your browser isn't even open? It's usually adware, spyware or scareware.
You can usually tell it's the last one if the pop up says "a virus was detected." It will offer you a paid program to remove the virus. Of course, you'll just be downloading even more malware.
Keep an eye on your email "sent" folder and on your social network posts. If you see items you didn't send or post, change your account passwords immediately. This will lock out a virus that's stolen your passwords.
Then go to work with your security software. After you've removed the virus, I'd change your passwords again, just in case.
Be sure to let your friends and family know you were hacked. That way they can take precautions for their accounts as well.
Having trouble taking back your account from a virus or hacker? Click here for detailed instructions to clean up your computer.
Locked computer
You're surfing the Web minding your own business. Suddenly a scary message appears. It says law enforcement has detected illegal material on your computer. You've been locked out until you pay a fine!
Of course it's a lie. A virus has taken over and is holding your computer ransom. That's why it's commonly called "ransomware."
Some ransomware doesn't even try to be sneaky. It tells you up front that hackers took over your system. You have to pay to get it back.
I don't recommend paying. You won't get your computer back.
Unfortunately, you probably won't be able to run your normal anti-virus program. You'll need a rescue CD. Click the links for the free AVG Rescue CD or Windows Defender Online to take care of the problem.
In some cases, the ransomware actually encrypts your files. If that happens, you better have a recent backup. Even if you get rid of the virus, your files might be lost.
Essential tools and programs stop working
If a computer is misbehaving, most computer users hit Ctrl + Alt + Del. The "three-finger salute" lets you open up Task Manager. This can show you what programs are causing trouble.
Sometimes, you'll hit this keyboard shortcut and nothing happens. Your Start Menu won't open. Nothing happens when you right-click on the desktop. Your security software won't run.
This is often a clue that a virus is messing with your computer. It's doing what it can to keep you from identifying it and removing it.
This is where deep-cleaning anti-malware software like MalwareBytes will shine. If that fails, you'll need to use a rescue CD like I mentioned earlier.
If nothing you do works, it could also be a hardware problem. Most likely it's bad RAM or a failing power supply.
Everything is running fine
I run into many people who don't install security software. The excuse is always the same: "But my computer runs just fine without it. If I had a virus, I'd know."
The simple fact is that you don't know. Modern malware can hide deep in your computer without raising red flags. It will just quietly go about its business.