During a House Judiciary Committee hearing on Wednesday (28 September), FBI Director James Comey revealed hackers have attempted to hack into voter registration sites in more than a dozen states and on several occasions. Investigators believe Russia is behind the attempted hacks, officials said.

"There have been a variety of scanning activities which is a preamble for potential intrusion activities as well as some attempted intrusions at voter database registrations beyond those we knew about in July and August," Comey said.

According to CNN, Comey told states to remain vigilant of their voter registration systems, warning that would-be hackers are "poking around".

He said: "We are urging the states just to make sure that their deadbolts are thrown and their locks are on and to get the best information they can from DHS (Department of Homeland Security) just to make sure their systems are secure. Because there's no doubt that some bad actors have been poking around."

The FBI director confirmed that the hacks had not been successful, although would-be hackers have still scanned and attempted to see if they can gain access.

Earlier in 2016, Russian hackers allegedly attempted to breach state voter registration databases in Arizona and Illinois. Officials said the breaches included the attempted theft of information from as many as 200,000 voter records in Illinois. In Arizona, hackers used malicious software to gain access to records but failed.

Illinois state officials said that no voter record had been altered or deleted, while state officials in Arizona noted that hackers were unsuccessful in breaching the system. "In no cases was information changed, nor were any actual voting systems at risk," Comey assured Congress.

Comey added that the FBI is looking "very, very hard" at Russian links to the hacks, reported Slate.

Homeland Security Secretary Jeh Johnson on Tuesday (27 Septmeber) said that 18 states had requested cyber assistance from the DHS regarding voting systems. Johnson called state election officials in August to urge them to look into how to better secure their systems.