Engine: Need advice

I have a 2006 Altima that just as of today doesnt want to start. I troubleshooted and came to the conclusion (by checking each one individually) that none of the 4 spark plugs are producing a spark. which leads me to my next point. if everythings turning over n working what would cause all 4 not to produce a spark. Theres a little black box on the side of the throttlebody (a relay box?) that is making a high pitched humm. does anyone know what this is and what if any sensors are connected to it. I opened the throttle body manually a couple times to ensure it wasnt stuck and it started for a brief min then died. so any help/info would be greatly appreciated thanks and sorry for the book but i tried to fit everything ive found up to this point.