Senrio has a blog post with a list of firmware security tips for IoT devices:
http://blog.senr.io/blog/5-tips-for-better-iot-and-firmware-security
5 Tips for Better IoT and Firmware Security
In this new wold of “the Internet of Things” and billions of networked embedded devices, it is crucial for device manufacturers to bake security into their new designs before they leave the factory. Here are five tips from a team of security researchers who make a living reverse engineering (hacking) into IoT devices on behalf of industry clients. […]
Firmware Security 