Hackers are increasingly targeting hardware and firmware as software security improves. The USB port, which is used for charging many devices, can also transmit malicious code or data if the device is plugged into a compromised public charger. Several types of USB attacks have been demonstrated, including installing malware, simulating keystrokes to steal login credentials, and damaging devices with power surges. Bluetooth and wireless vulnerabilities have also been exploited by hackers to gain remote access to devices within range. Medical devices are a major concern as vulnerabilities have been shown that allow full wireless control of insulin pumps and ability to remotely trigger shocks from implanted pacemakers and defibrillators.