Most of your holiday shopping will likely be done online. Thieves know it and might be waiting on a website you visit.
Ken Colburn with Data Doctors says it's called "drive-by downloads."
"Stuff can sneak into your computer behind the scenes when you visit certain websites that have either been compromised or set up to be malicious websites," Colburn says.
And there are likely more dangerous sites during the holidays when hackers know you're shopping.
However, Colburn says even visiting legitimate sites could be an issue.
"You can't trust all websites just because they look mainstream," he warns.
You can also get into trouble by clicking on certain ads. Once they're in, hackers could invade your computer remotely.
The browser you use to visit online sites is what hackers target.
"Looking for missing updates so they can get around the security that has been built in," Colburn says.
To protect yourself, updating your browser, operating system, and all software is crucial.
"You get the added benefit of all these security tools that are being added all the time," he says.
To check for browser updates, do a Google search for "updating browser" using your browser name. With Google Chrome, you can type this: Chrome://settings/safetycheck.
Read more from Data Doctors about protecting your computer.
To keep you safe when clicking on ads, you can install an ad blocker.