WASHINGTON -- A new report shows that 24 states are using voting systems for overseas and military voters that could be vulnerable to hackers.

Those states let overseas voters return their ballots using the Internet, email or fax, which could fall victim to cyberattacks.

The report also shows that polling places in 16 states use paperless machines, so there's no paper record in case of a recount. Other states don't have proper backup plans or audit procedures in place.

Colorado, Delaware, Kansas, Louisiana, Mississippi and South Carolina are the six states least prepared for voting problems. Minnesota, New Hampshire, Ohio, Vermont and Wisconsin are best prepared.

Common Cause, Rutgers Law School and the Verified Voting Foundation teamed to produce the report.