avengers: maria hill

You know I love to crowd-source my fic

Can someone help me figure out what SHIELD actually does? What are their day-to-day missions like? What kind of security threats are they confronting? What do they do when there's not an alien invasion?
I've always thought their day to day focus is to keep bad situations from getting worse. Drug smuggling, kidnapping, weapons trafficking. But underneath that is the real purpose -- unexplained phenomena, development of weapons or means of protection from unexplained threats (remember, SHIELD was started by Howard Stark, and Nick Fury after Red Skill appeared and they developed the serum that "made" Captain America during WWII.

I love their purposely vague acronym.
Thank you! You've given me a lot of ideas! I'm glad I'm not the only one who imagines some kind of "every day" bad situations in addition to the paranormal science fiction-y stuff.
Espionage? Undercover work to bust up drug and/or sex slave rings? Play World of Warcraft and/or Diablo?
I would imagine any threat that has to do with advanced science or meta human groups. Groups similar to HYDRA, people attempting to make serums to 'enhance', genetic experiments, attempting to create animal/human hybrids...why yes I have been watching Teen Wolf and Buffy how did you know?

Also, since I haven't seen it in fic yet, I would think they would run drills...in the form of war games. A la stargate command.
"What do they do when there's not an alien invasion?"

In my experience with most places (though admittedly not alien invasions)... try desperately to finish up the paperwork that resulted from the LAST alien invasion.