2016 Postmortem

"One form of wholesale fraud possible with optical scan voting systems is during the recording of votes. Douglas W. Jones of the University of Iowa states that if a potential attacker were to gain access to the voting system configuration files, they would be able to "credit one candidate with votes intended for another." He found these files are exposed in the computer system used to prepare the election, making them vulnerable to anyone setting up the election. The files are then transferred to the voting system using removable media, and "anyone with access to these media could potentially attack the system."[15]

Another form of wholesale fraud is during tabulation. Possible attacks have been demonstrated by Harri Hursti[16] and the University of Connecticut.[17]

If an attacker is able to obtain a blank ballot (by theft, counterfeit, or a legitimate absentee ballot) the attacker can then mark the ballot for their chosen candidates and convince (through intimidation or bribery) a voter to take the pre-marked ballot to a polling station, exchange it for the blank ballot issued and return the blank ballot to the attacker. This is known as chain voting[18]"