You need to start by using a full disk encryption (FDE) mechanism. Something like BitLocker for Microsoft or FileVault for Mac or any others. edit: do not store your recovery key on the same pc.
That is your base line defense but it is certainly not enough for total protection.
To be perfectly honest, you need to change your behaviours in order to be very secure. For instance:
- If possible, do not travel with all of the code.
- Consider using a secure VPN to access your sensitive info (that leads to other threat vectors though).
- Limit your exposure in threat zones, keep your laptop with you.
- Do not hibernate your computer (always turn it off and on). edit: hibernation may be ok (personally I do not trust it -but I have an SSD so what's the real difference). Stand-by or sleep mode is the real issue in regards to cold boot attacks.
- As an aside to the cold boot attack vector, you may want to look here for info on how to safegaurd against cold boot attacks.
- Be alert in general.
- Change your passwords frequently.
- Never access public wifi
- Disable bluetooth and wifi (if possible and when not using it)
- You could also look into a remote wipe software/service (but it's not perfect).
- Disable Ad Hoc Connections as this is potentially a huge risk.
update: Others have mentioned the bios. You can enable a password there and disable booting from removable media but the bottom line is that if an attacker has your pc in their hands, your only line of protection might very well be FDE. Here is an article about bios protection.
