Energy theft and meter tampering are world-wide problems that contribute heavily to revenue losses. Consumers have been found manipulating their electric meters, causing them to stop, under-register or even bypass the meter, effectively using power without paying for it. Apart from preventing physical tampers requiring smart solutions on chip, smart grid technologies are now in the process of being deployed. These solutions require a combination of different technologies and rely on network connectivity, posing significant security issues that must be addressed from the beginning. This paper covers vulnerabilities, challenges and techniques to prevent tampering in an energy meter, improving overall security (hardware and software) in a smart grid.