The most common signs that your computer has been compromised by malware are:
- Slow computer performance
- Browser redirects, or when your web browser takes you to sites you did not intend to visit
- Infection warnings, frequently accompanied by solicitations to buy something to fix them
- Problems shutting down or starting up your computer
- Frequent pop-up ads
The more of these common symptoms you see, the higher the likelihood your computer has a malware infection. Browser redirects and large numbers of pop-up warnings claiming you have a virus are the strongest indicators that your computer has been compromised.