American researchers have proven it's possible to maliciously turn off individuals' heart monitors through a wireless hacking attack.
Many thousands of people across the world have the monitors, medically known as implantable cardiac defibrillators (ICDs), installed to help their hearts beat regularly.
ICDs treat abnormal heart conditions; more recent models also incorporate the abilities of a Pacemaker. Their function is to speed up a heartbeat which is too slow, or to deliver an electrical shock to a heart which is beating too quickly.
According to the research (pdf) by the Medical Device Security Center - which is backed by the Harvard Medical School among others - hackers would be able to intercept medical information on the patient, turn off the device, or, even worse, deliver an unnecessary electrical shock to the patient.
The hack takes advantage of the fact the ICD possesses a radio which is designed to allow reprogramming by a hospital doctor. The ICD's radio signals are not encrypted, the Security Center said.
The Security Center demonstrated the hack on an ICD made by Medtronic using a PC, radio hardware and an antenna. The ICD was not in a patient at the time. The research is detailed in a report released today.
The report reveals that a hacker could "render the ICD incapable of responding to dangerous cardiac events. A malicious person could also make the ICD deliver a shock that could induce ventricular fibrillation, a potentially lethal arrhythmia."
The Security Center says manufacturers of ICDs could implement several measures to prevent the threat. These include making the IMD produce an audible alert when an unauthorised party tries to communicate with their IMD. It also suggests employing cryptography to provide secure authentication for doctors.
The researchers added that the risk facing patients is negligible. "We believe the risk to patients is low and that patients should not be alarmed," it said in the report.
"We do not know of a single case where an IMD patient has ever been harmed by a malicious security attack."
It added that hackers would need to be physically close to their intended victim and would need sophisticated equipment. The kit used in the demoed attack cost $30,000.
The researchers omitted their methodology from the paper to help prevent such an attack ever happening, they said.
Medtronic said the chance of such an attack is "extremely low". Future versions of its IMDs, which will send radio signals ten metres, will incorporate stronger security, it told the Associated Press. ®