Pacemakers send and receive signals and it seems that pacemaker transmitters can be reverse engineered. This means that criminals can hack them and make them send a high voltage electric shock to pacemakers. The most scary part is that this can be done wireless and the attackers can be anywhere within few meters range. The distance can vary with different antennas and different environment (walls, windows, etc). It is also possible to change the firmware of a pacemaker and create some king of virus which will spread from pacemaker to pacemaker. The creator of the firmware can make the pacemakers to send a deadly shock and kill many people with a single click. The most scary part is that this is not a science fiction and the security of pacemakers needs to be increased.
Source: [Science Magazine]