In most cases, this comes down to a momentary hiccup in the software, which is why rebooting a computer fixes so many problems. It could also be another software or hardware problem you can fix yourself, if you know what to do. However, it might go deeper.
1. Pop-up ads
Running into a pop-up ad while you're surfing used to be a serious annoyance, but modern browsers include pop-up protection to keep these annoyances away on most sties. If you're still seeing regular pop-ups on more than one site, it could just be a badly-configured browser.However, if pop-ups are coming at you when your browser isn't even open, it's likely you have a virus. This is especially true if the pop-ups advertise some magic cure-all to your "virus woes"
If you are bombarded with pop-up ads, first run a scan with anti-spyware software to double-check. I like SpyBot Search & Destroy because it digs deep into your settings to find any problems spyware has left behind.
2. Messages you didn't send
Most viruses have one goal in mind once they infect your computer: to spread the virus as far as possible. An easy way to do that is to send messages to as many of your friends as possible in hopes they'll get infected, too.These messages can show up anywhere. The virus might try to send out spam through your email account. It could take control of your Facebook or Twitter and send out spam, too. In almost all cases, it will include a link or attachment to the virus somewhere in the post.
Keep an eye on your email's "sent" folder and on your social network posts. If you notice emails and posts that you don't remember sending or posting, it's likely that you have a virus. Here is what you need to know to take your account back.
3. You're locked out of your computer
You're surfing the Web when suddenly a scary message appears saying you're locked out of your computer. It may claim to be from law enforcement or an anonymous blackmailer.Either way, the program is lying. What's really happening is that a virus is blocking important programs from running, or even encrypting your files so you can't get to them. The scam is trying to make you pony up some cash to get your computer back. That's why it's commonly called "ransomware."
4. Programs and tools are out of reach
More often than not, a computer user will rely on one simple command when their computer starts misbehaving: Ctrl + Alt + Del. The "three-finger salute" opens up Task Manager, which can tell you so much about your computer.Sometimes, however, you'll hit this keyboard shortcut and nothing happens. You might get a random error message, too. This is a dead giveaway that a virus is messing with your computer. It's stopping Task Manager so you can't see that it's eating your system resources or shut it down.
A virus might block any number of programs or utilities to try to protect itself. This is where deep-cleaning anti-malware software like Malwarebytes will shine. It goes much deeper than most anti-virus software to clean out your computer. Plus, it has a feature that helps it get around viruses that block popular anti-virus programs from running.
5. You're not seeing any symptoms at all
No news isn't always good news when it comes to viruses. Powerful viruses can hide deep in your computer without raising any red flags. They'll just go about their business without you even knowing they're there.Just because you don't notice them doesn't mean they aren't dangerous, though. They could be snagging your passwords, sensitive files or other vital information from your computer. The virus could be using your computer to spread to other computers or even attack banks and other organizations.
The only clue in this case might be a slower Internet connection since the virus is using it. Click here to test your Internet speed and learn what to do if it's slower than it should be.
Your computer's processor and memory could also be running really high for no good reason. Click here to track down misbehaving programs and potential hidden viruses.
I do know some people who don't bother installing security software because their computer doesn't seem to have a problem. If that's you, let me tell you that you probably do have a virus. Every computer user, even Mac users, needs security software running at all times.