Answer from cs61c-bg (Spencer Ahrens 16187781) for Question 1
I don't remember and, looking back, couldn't find anything about security holes in the reading, but the best I could think of would be programmers hiding viruses in programs that are disguised as some innocuous file type, then calling them as mips instructions.  Saving the code for a jump call to itself in a register as a 32 bit number, then loading it as code could crash a computer in an infinite loop.  Possible prevention technique could be to always have a "big brother" application watching the processes of all applications, prepared to shut them down if they crash (ie the operating system).  This sacrifices speed and memory.