Recently, a burglar attempted to break in to my apartment by coming up the fire escape and pry open the window. Lucky I heard him and he was scared away when I turn on the light. My apartment is on the second floor of a four story walk-up building. The fire escape is in the backyard connected to each floor and meant to be access through the window. Obviously, install bars outside is not possible due to fire code. What are some of the things I can do myself or products to buy to secure the windows against intruders?
You could pick up a magnetic window/door alarm (some more expensive models may also have glass break sensors).
If the window is opened, the alarm will sound.
Secure the window
You could purchase, or make a "security bar" similar to the ones used for sliding doors.
This will make it more difficult to open the window, though would not protect against breaking the glass. If you make/purchase an adjustable version, you would even be able to leave the window open slightly and still be protected (as long as it's not open enough for the intruder to slip in).
Protecting the glass
There are many companies that make Security Window Films, that can be applied to glass to make it "unbreakable".
Depending on your budget for this project, a combination of these products would be the best solution.