The following was a post I had done on another site awhile back.

IDENTIFYING AND PROTECTING YOURSELF FROM SCAREWARE AND MALVERTISING TACTICS:

Malvertising is no new internet scam tactic, but since an increasing number of people are using smartphones these days the style of malvertising has adapted considerably, and consumers need to know what they could face while browsing on their mobile devices. As the name would suggest, malvertising is a form of malware that could either trick a user into sending money to an address for bogus antivirus software or encrypt files on a smartphone/computer and hold said files for ransom. This particular form of online scam is called scareware, and it's becoming more common than ransomware.

While browsing on certain sites you may get a pop-up ad claiming you have accidentally downloaded a virus (or multiple viruses) and immediately need to download the antivirus software that the ad is displaying. Another type of scam would claim your smartphone battery is outdated and needs to be upgraded. These type of pop-ups can be aggressive, they are difficult to exit out of and all the while may even cause your device to beep loudly and vibrate, which would panic most people. The ironic part is, if you were to do what the pop-up asks you to do, you run the risk of actually downloading a real virus that could gain access to just about every file/app on your device. In other words, the pop-ups are lying about you having downloaded a virus in an attempt to get you to download their software which in most cases is a virus, and will even make your device beep to scare you.

If you are ever faced with this sort of scam, DO NOT do as it prompts you to do, immediately close out your browser tab. If that is not enough, go to the list of apps in the settings and find the browser app you had used and find the app's cache details and clear it, and it may even be necessary to force stop the app too. That should resolve the issue, and the next time you go to open the browser app it should be okay. On a laptop or desktop pc, minimize the browser window and open up the task killer to halt the browser's activity. As mentioned before, these types of malware can be aggressive and make your device either beep loudly or vibrate or a combination of both. If a task killer isn't good enough, then press Ctrl-Alt-Del all at once to restart the computer.

Hope this post was helpful.