Researchers from US-based cyber security firms Anomali Labs and Intel 471 discovered the huge cache on the dark web – a hidden section of the internet used by cyber criminals.
The records, posted to a popular hacking forum, included personally identifiable information such as the voters' full names, phone numbers, physical addresses and voting history.
The researchers noted that the records did not necessarily originate from a hack, but rather could have been obtained by someone who has legitimate access to the databases, such as a government official.
"To our knowledge, this represented the first reference on the criminal underground of actors selling or distributing lists of 2018 voter registration data, including US voters' personally identifiable information and voting history," they stated in a report.
"With the November 2018 midterm elections only four weeks away, the availability and currency of the voter records, if combined with other breached data, could be used by malicious actors to disrupt the electoral process of pursue large-scale identity theft."
Ways in which the data could be used to disrupt the elections include deleting voting registrations, changing voters' addresses, or requesting absentee ballots on behalf of the legitimate voter.
The voting records come from at least 19 US states, including: Georgia, Idaho, Iowa, Kansas, Kentucky, Louisiana, Minnesota, Mississippi, Montana, New Mexico, Oregon, South Carolina, South Dakota, Tennessee, Texas, Utah, West Virginia, Wisconsin and Wyoming.
The price for the data of each voter list varies from $150 to $12,500 depending on the state, the researchers said.
"This pricing model could be related to the number of voter records per database listing and/ or, to a lesser degree of confidence, to offset the original cost to the illicit vendor," the report states. "Once purchased, the vendor claims to provide customers with regular updates at the start of each week."
The voter record listing claims to contain the details of 23 million voters in Louisiana, Wisconsin and Texas (Anomali Labs)
One of the voter record lists has already been made publicly available through the hacking forum, after a crowdfunding campaign was set up to purchase the entire database of Kansas.
A separate report published by dark web intelligence company Terbium Labs this week detailed how increased profits for cyber criminals has accelerated the "professionalisation" of fraud.
The report explained how leaked and stolen personal data can pass through a highly-sophisticated supply chain to carry out a variety of crimes.
"Fraud is a multi-step process, and the dark web has accelerated the professionalisation of fraud to make these tools popular, affordable, and accessible," said Munish Walther-Puri, chief research officer at Terbium Labs.
“There continues to be an increase in the variety and volume of goods and services offered in this underground economy... The fraud community is built on the trade of ill-begotten sensitive data and is highly developed, with infrastructure, operations, business models, and proﬁt margins."
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