(CBS News) Concerns are growing over the possibility of a rigged presidential election. Experts believe a cyberattack this year could be a reality, especially following last month's hack of Democratic National Committee emails.

The ranking member of the Senate Homeland Security Committee sent a letter Monday to the Department of Homeland Security, saying in part: "Election security is critical, and a cyberattack by foreign actors on our elections systems could compromise the integrity of our voting process."

Roughly 70 percent of states in the U.S. use some form of electronic voting. Hackers told CBS News that problems with electronic voting machines have been around for years. The machines and the software are old and antiquated. But now with millions heading to the polls in three months, security experts are sounding the alarm, reports CBS News correspondent Mireya Villarreal.

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