2016 Green Party presidential nominee Jill Stein launched a campaign on Nov. 22, 2016 to initiate recounts in battleground states Wisconsin, Michigan, and Pennsylvania. She stated that the recount campaign was “a multi-partisan effort to check the accuracy of the machine-counted vote tallies in these states in order to ensure the integrity of our elections.” Stein is especially concerned with potential hacking efforts because the voting machines used are allegedly especially vulnerable to security attacks. Ajamu Baraka, Stein"s running mate, stated, “I am not in favor of the recount” because “it was a potentially dangerous move” that could “be seen as carrying the water for the Democrats.”
Concern about the security of voting machines is not new but was compounded in the 2016 election by hacks into the Democratic National Convention and leaks of over 40,000 emails by WikiLeaks. Admiral Michael Rogers, Director of the National Security Agency, and James Clapper, Director of National Intelligence, stated the hacks were carried out by Russians. Further, there is evidence of an attempt to hack voter databases in Arizona and Illinois by hackers with Russian IP addresses.
The Clinton campaign had been encouraged to file for recounts by computer scientists and election lawyers who found that Clinton may have been denied as many as 30,000 votes in Wisconsin (she lost the state by 27,000 votes) because she received 7% fewer votes in districts that use electronic voting machines, compared to those using optical scanners and paper ballots. The Clinton campaign joined Stein’s efforts on Nov. 26, 2016 after it was announced that Wisconsin would recount their votes on Nov. 25. Hillary Clinton’s counsel, Marc Elias stated that the campaign had had no plans to initiate a recount themselves because “we had not uncovered any actionable evidence of hacking or outside attempts to alter the voting technology."
Source: procon.org

Originally developed in the 1970s, direct recording electronic (DRE) voting machines have become increasingly used nationwide. After the 2000 US presidential election’s troubles with “pregnant” and "hanging” chads and the subsequent passage of the 2002 Help America Vote Act which swelled use of DREs, electronic voting technology became widely debated.
ProCon.org announces its new video about the pros and cons of electronic voting machines. After the “hanging chad” paper ballot debacle in the 2000 Bush-Gore elections, direct recording electronic (DRE) machines, often called electronic voting machines, became increasingly popular. DREs were used in 39% of all US precincts in the 2012 presidential election.