Q: I've been getting a pop-up at the bottom of my screen that says, "Do you want to open or save ImgSync from image8.pubmatic.com?" My choices are open, save or cancel. I've clicked "cancel" or just closed the message box without responding, but the message always comes back. I've run the Malwarebytes security software and another program called "Computer Cleaner," but neither finds any malware to delete. What is this thing, and how can I get rid of it?
Lana Luhm, Eau Claire, Wis.
A: Your Norton antivirus software is protecting you from advertising malware. You were right to click "cancel," saying "no" to the download.
That should have been the end of it. The recurring message means the malware is trying again and again to download to your PC. And that indicates the malware is coming from a website that you visit frequently.
The website that's identified in your message belongs to Ads.pubmatic.com, a service that distributes advertising from many different companies to websites. However, some unscrupulous companies use the ad distribution service to place malicious software on otherwise legitimate websites. This malicious software is called "drive-by" malware because it automatically tries to download to any computer that visits the infected site.
Because your PC doesn't appear to be infected yet, you can protect yourself against future download attempts by installing a free security add-on for your browser. The most popular one, Adblock Plus, blocks dangerous or intrusive ads (tinyurl.com/klmoy35).
For the benefit of other readers whose PCs may already be infected, Norton-maker Symantec Corp. suggests using the program to run a "full system scan" that should find any installed malware and delete it. As a second line of defense, Symantec recommends running the free version of Malwarebytes (see tinyurl.com/jsdacdk).
If Norton and Malwarebytes together can't do it, try an alternate removal method that involves using your PC's Control panel to uninstall any suspicious programs, then running Malwarebytes and the free versions of two other security programs, HitmanPro and AdwCleaner (see tinyurl.com/ya2djnvp).
