This year's challenge story centers around hackers attacking critical "supervisory control and data acquisition" (SCADA) infrastructure. Your mission, should you choose to accept it, is to figure out how the SCADA network is being attacked, find the attack vector(s), and stop the bad guy(s)/gal(s)/other(s).
Codebreaker-Challenge is unusual for capture-the-flag(ish) contests due to the scope/number of challenges and how long the contest runs (now until end of year). Also (this year, at least), the challenge is built around a less than well-known networking protocol, MQTT. It's open to anyone with a school.edu email address. A site leader-board shows which school/University has the most l33t students. Carnegie Mellon and Georgia Institute of Tech are at the top of the leader-board as of Saturday morning.
Last year, 3,300 students (from 481 schools) participated, with 15 completing all six tasks. One Carnegie Mellon student finished in less than 18 hours.
A resources page offers "information on reverse engineering," and the NSA says the first 50 students who complete all the tasks ths year will receive a "small token" of appreciation from the agency.