The linked video should not stand as proof that the hack can be done. Note that they boot the machine with, supposedly, a memory card that loads the software. The machine must be left powered for the new 'ware to run, and rebooting the machine with the
correct card will load the real software when the machine is rebooted. Unless, of course, the felon has "simply" opened the machine and replaced the boot eeprom with a fake copy.
The report mentioned in the video does state that there are security seals on the memory cards, locks, boards, and so forth but references another report that says that these seals are not always checked.
So the simple solution is to check the seals before an election, and always assure that the machine is booted with the correct card, then have its port sealed with a new security seal.
If there are questions, the malware will stay installed on either the tampered card or in the boot eeprom (unless it is bright enough to know that it has been moved to an FBI Forensic Computer Lab and deletes itself), and the forensic examiner will find it (if the operating system can boot it, a human can find it too). At that point, a criminal investigation begins. If the malware can be decompiled, the vote shifting algorithm can be determined and the vote count corrected. At worst, the machine's count can be discarded like badly voted paper ballots.
As for a virus spreading from machine to machine through a LAN, why then, let's install firewalls and virus checkers in the lan! And let's ask a third party virus company to make a virus/malware checker memory card for the voting machine while we are at it.
Where I vote, with paper ballots, the boxes all have seals.
Another thought- the video images offer no proof whatsoever that the voiceover is correct.