This appears to be a very easy and effective attack on election systems that does not even involve trying to flip votes.
"The center also distributes the voter registration list to counties for use on their ExpressPoll pollbooks; if attackers were to delete voter names from the database stored on the center’s server or alter the precinct where voters are assigned, they could create chaos on Election Day and possibly prevent voters from casting ballots. This is not an idle concern: During the presidential election last year, some voters in Georgia’s Fulton County complained that they arrived to polls and were told they were at the wrong precinct. When they went to the precinct where they were redirected, they were told to return to the original precinct. The problem was apparently a glitch in the ExpressPoll software."
In other words, the very system that had major security problems and a lack of due diligence in fixing them, maintains the "source of truth" for the per-precinct registration lists. Merely deleting voters from lists in precincts which are known to lean towards one party or the other would probably be enough to tip an election (even if they are allowed to vote provisionally, that doesn't always go smoothly, and it always slows things down and creates confusion; if you can get them shuttling between precincts through manipulating the files, even better.)
This is an attractive attack vector because it's easy, it doesn't require attacking voting machines at all, could be done by attacking a "low security" system, and could be blamed on "glitches" quite plausibly. And we already know from the leaked report last week that state-level actors were attempting to modify voter roll information in other systems.
[This was originally published Jun 14, 2017 at https://plus.google.com/115608553892438743738/posts/QxYGgrETgwh]