I would second this. We know for a fact that the NSA uses BIOS malware. I don't believe we know for a fact that such malware is routinely installed by border guards, but it's not a very far-fetched worry at this point.
The technical expertise required to do so is very limited as long as you don't password-protect the BIOS: Basically, they only need to be able to plug in a USB stick and reconfigure the BIOS to boot from it.
In other words: If you leave your laptop outside of your physical control for even a few minutes, you may have to assume that it is totally compromised as long as you don't have a BIOS password.
If the laptop is outside of your control for a longer period of time, you probably have to assume that it has passed through the hands of somebody with sufficient technological know-how to work around the BIOS password as well.
The technical expertise required to do so is very limited as long as you don't password-protect the BIOS: Basically, they only need to be able to plug in a USB stick and reconfigure the BIOS to boot from it.
In other words: If you leave your laptop outside of your physical control for even a few minutes, you may have to assume that it is totally compromised as long as you don't have a BIOS password.
If the laptop is outside of your control for a longer period of time, you probably have to assume that it has passed through the hands of somebody with sufficient technological know-how to work around the BIOS password as well.