My concern just stems from hearing about Snowden and all the crazy stuff hackers can do
Many people forget that there is a huge number of firmwares in any modern computer. Even if you replace a logic board and SSD, there are still a lot of peripheral devices - like webcam and touchpad ; even a keyboard sometimes has a tiny firmware! So there is a possibility for the professional hackers to create a powerful malware (some kind of BadBIOS -
https://arstechnica.com/security/20...erious-mac-and-pc-malware-that-jumps-airgaps/ ) , which will be able to hide not just in EFI/BIOS firmware storage chip but also at the firmwares of peripheral devices - so that, in case someone will replace a logic board or reflash EFI/BIOS by an external hardware programmer, this malware could emerge from its' hiding place and re-infect the computer at the next or after a few reboots...
But I mean company trade secrets are a whole different ball game.
This kind of attack is not easy to perform - and even if a prior owner of that refurbished MBP is a hacker which already has this malware in possession, he will think twice before infecting it and returning to Apple - because, if this malware would be discovered, this will link it to a previous owner. However, a rogue Apple employee could also try to do that
its all new firmware/cpu/ssd/display etc.
Unless they give you a completely new MBP (in which case it wouldnt be refurbished) there will be at least 1 programmable chip remaining from a previous owner, where the malware could reside
<MBP> is as safe as any other computer
I would not say that, because Apple is collaborating with NSA and they lied about patching the security holes, while they haven't been patched --- (spotted by WikiLeaks) . If Apple leaves the backdoors for NSA, any other hacker could discover them and use as well
There are computers which are more safe than MBP - I am talking about those rare desktops/laptops which are supported by coreboot project and have open source BIOS which you can personally verify that it doesn't contain any backdoors and rebuild by yourself. Also install a completely open source operating system like Trisquel Linux (no closed source drivers!) and spend a sh!tload of time to constantly harden its' security (all kind of encryptions, hardened software settings, manual patching against the exploits, etc.) . But for a person who even thought that MBP are safe for top secret info, this seems like an impossible quest...