Since December, hundreds of millions of voters in the U.S., the Philippines, Turkey and Mexico have had their data discovered on the web in unprotected form. In some instances, legitimate security researchers found the information, but in others, malicious hackers are suspected of pilfering the data for criminal purposes.

The data breaches are raising questions as the U.S. considers whether to move toward electronic balloting. More people than ever are using the internet to register to vote and to request mail-in ballots. Some states have even become vote-by-mail only in recent years. 

"If you can't keep the voter registration records safe, what makes you think you can keep the votes safe?" asked Pamela Smith, president of election watchdog Verified Voting.