Any byte in the machine, or...
...any byte in your process's address space? (I assume that my process cannot touch your process's stuff...)
shrub\ufffdbish (Am., from shrub + rubbish, after the derisive name for America's 43 president; 2003) n. 1. a form of nonsensical political doubletalk wherein the speaker attempts to defend the indefensible by lying, obfuscation, or otherwise misstating the facts; GIBBERISH. 2. any of a collection of utterances from America's putative 43rd president. cf. BULLSHIT
As much protection as the Operating System provides...
...which for Windows is to say None At All. Unmanaged code is the umbrella of native code that's not managed within the sandbox. All those VBX or COM or COM+ or DCOM things can be invoked within the unmanaged state.