Some information of roughly 90,000 Illinois voters was accessed in the breach, down from an estimated 200,000 earlier this week, according to an update from the Illinois State Board of Elections.
According to the release, officials have determined the records of about 700 specific voters were accessed, and those people will soon be notified.
The board also said that 86,000 records were "strongly suspected to have been viewed." The state is in the process of identifying those people to notify them, the release said, but added that just over 3,500 records will be unidentifiable for an unspecified reason.
The update also said officials were "sure" that "no records have been altered or changed in any way."
After news broke earlier this week that state election agencies in Illinois and Arizona were targets of hacking, likely by a foreign entity according to a US official, concern grew about a potential impact on elections of cyberattack.
But Illinois has lowered its estimate of how many voters' information may have been affected, and the impact has been minimal in both states. Illinois said that of the records accessed, it's possible hackers might have obtained voters' name, address, date of birth, driver's license number or last four digits of their Social Security Number.
Voter rolls and state records are attractive targets for hackers, who often make money by stealing personal information of unsuspecting individuals and then selling off those records on the dark web for us in identity theft and financial crime.
There were rumors in Arizona that the hack was attributed to a Russian-based source, but the secretary of state's spokesman told CNN it was based on indirect knowledge.
Russia and Eastern Europe have a high percentage of the active financially-motivated cybercriminals in the world.
The hack had raised extra concerns, however, because attackers believed to be connected to the Russian government hacked Democratic political organizations earlier this year, dumping a trove of emails and documents online in what experts believe is an effort to influence the US election.
There has been no indication that the events are related to date.