One security researcher discovered the password protecting the microcontroller in MacBook batteries is not unique for every notebook and is easily hackable. It could brick your battery, or worse, install malware that's nearly impossible for the average person to scrub.
TDSS is a trojan virus that infects computers and installs the TDL-4 program, which makes said computer part of a botnet 4.5 million machines strong. TDL-4 is extremely difficult to detect and eliminate. One expert at Kapersky Labs says TDL-4 is "practically indestructable."