The U.S. firm Johnson & Johnson, one of the biggest manufacturers of medical appliances, warned this week that its insulin pumps could be hacked, meaning unauthorized persons might be able to change insulin doses of thousands of diabetes patients. The vulnerability affects only pumps that have wireless remote control, which uses unencrypted radio frequencies, but they are not connected to the internet. Recently it was revealed some pacemakers and defibrillators also may be open to hacking. The company said the probability of unauthorized access to its insulin pumps "is extremely low," but it has nevertheless sent warnings to doctors' offices and more than 100,000 patients in the United States and Canada. Insulin pumps are wearable devices that automatically adjust the release of insulin according to a diabetic's level of physical activity.