Someone explain to me how voting machines can be hacked

[Pyro]

Trump's 400lb hacker can break into anything.

[IceAgeComing]

Voting machines cannot be hacked, this nonsense was invented by Trump. 

ANYTHING can be hacked.

Yes, this is technically true but its much easier to hack into something like a PC connected to the internet rather than a closed off system like a voting machine since you have more ways of getting into it - the only way to put dodgy code in is by physically interacting with the machine since there'll be no network access, and that's hard to do in a very exposed public space like a polling station.

Although I'm personally a "do everything on paper" guy myself: or at least have the computer output some kind of printed ballot that can act as a check for a recount of a close election or backup if there's some kind of technical problem.  A perfect solution for people with disabilities that make old fashioned paper ballots very hard but if you wanted to keep a paper-based system would be to have machines available that printed a paper ballot out, with that being checked by the voter before it is submitted and then used in the count so everyone can guarantee that it was 100% correct.

[Andrew]

What you are describing is a voter-verified paper audit trail.  Most (but unfortunately not all) states that use electronic voting machines now require this.

If Ohio didn't have this paper trail, I wouldn't go to the polling place to vote; I'd request an absentee ballot in the mail.  Without the voter-verified paper audit trail, the electronic voting machines are not to be trusted.

[136or142]

I don't know if the voting machines can be hacked or not, but that's an incredibly inefficient and rather pointless way of trying to change the election outcome.  

The way any hacker with any intelligence would do it is to hack each county's and/or each state central database where the votes are stored.  The elections people say these databases aren't hooked up in a way where an outside server can hack them, but I've also heard otherwise from people who I regard as credible, so I don't know who is telling the truth.

[Lachi]

Whatever was wrong with putting a cross on a piece of paper and then counting these?

Nothing. With appropriate processes (secured and tracked ballots and boxes with a verified paper trail, all overseen by multiple election officials and partisan observers) its the best election process there is.

But it doesn't produce results the media can report before everyone goes to bed on election night, so we make compromises in security for the sake of cool news coverage and a swift result.

Australia uses pencil, and paper, and we can get results really quickly even with preferences