Here is a direct quotation from this report, describing some of the ways by which the next election could be stolen (most footnotes removed) . . .
"To carry out these attacks, the attacker must somehow install his malicious software on one or more voting machines. If he can get physical access to a machine for as little as one minute, he can install the software manually. The attacker can also install a voting machine virus that spreads to other machines, allowing him to commit widespread fraud even if he only has physical access to one machine or memory card.
2.2.1 Direct Installation
"An attacker with physical access to a machine would have least three methods of installing malicious software. The first is to create an EPROM chip containing a program that will install the attack code into the machine's flash memory, and then to open the machine, install the chip on its motherboard, and reboot from the EPROM.
"The third method exploits a service feature of the machine's bootloader. On startup, the machine checks the removable memory card for a file named fboot.nb0. If this file exists, the machine replaces the bootloader code in its onboard flash memory with the file's contents. An attacker could program a malicious bootloader, store it on a memory card as fboot.nb0, and reboot the machine with this card inserted, causing the Diebold bootloader to install the malicious software. (A similar method would create a malicious operating system image.)
"The first method requires the attacker to remove several screws and lift off the top of the machine to get access to the motherboard and EPROM. The other methods only require access to the memory card slot and power button, which are both behind a locked door on the side of the machine. The lock is easily picked -- one member of our group, who has modest locksmithing skills, can pick the lock consistently in less than 10 seconds. Alternatively, this slot can be reached by removing screws and opening the machine. Some attackers will have access to keys that can open the lock -- all AccuVote-TS machines in certain states use identical keys, there are thousands of keys in existence, and these keys can be copied at a hardware or lock store.
"A poll worker, election official, technician, or other person who had private access to a machine for as little as one minute could use these methods without detection. Poll workers often do have such access; for instance, in a widespread practice called 'sleepovers,' machines are sent home with poll workers the night before the election.
2.2.2 Voting Machine Viruses
"Rather than injecting code into each machine directly, an attacker could create a computer virus that would spread from one voting machine to another. Once installed on a single 'seed' machine, the virus would spread to other machines by methods described below, allowing an attacker with physical access to one machine (or card) to infect a potentially large population of machines. The virus could be programmed to install malicious software, such as a vote-stealing program or denial-of-service attack, on every machine it infected.
"When the machine is rebooted, it normally emits a musical chime that might be noticed during a stealth attack; but this sound can be suppressed by plugging headphones (or just a headphone connector) into the machine's headphone jack.
"Diebold delivers software upgrades to the machines via memory cards: a technician inserts a memory card containing the updated code and then reboots the machine, causing the bootloader to install the new code from the memory card. This upgrade method relies on the correct functioning of the machine's bootloader, which is supposed to copy the upgraded code from the memory card into the machine's flash memory. But if the bootloader were already infected by a virus, then the virus could make the bootloader behave differently. For example, the bootloader could pretend to install the updates as expected but instead secretly propagate the virus onto the memory card. If the technician later used the same memory card to 'upgrade' other machines, he would in fact be installing the virus on them. Our demonstration virus illustrates these spreading techniques.
"Memory cards are also transferred between machines in the process of transmitting election definition files to voting machines before an election. According to Diebold, 'Data is downloaded onto the [memory] cards using a few [AccuVote] units, and then the stacks of [memory] cards are inserted into the thousands of [AccuVote] terminals to be sent to the polling places.'