Unfortunately the missions have finished for this year (unless the Directorate have got something hidden up their sleeve). The next ones will probably start much later in the year, but keep an eye out.
The Directorate will post a mission briefing on the briefings page. This will contain cryptic clues, which will send us all on a merry chase across the internet, through a myriad of specially created sites, using a variety of technologies old and new (this year the missions required gopher, an Apple Remote, access to a PC or debug mode in Safari, the Brainf*ck language, short-time fourier transforms, genetics and more). The goal of a mission is to discover the code to the safe, which when entered correctly is unlocked giving you some shiny loot.
It's a bit like a cryptic crossword on something illegal. Difficult, slightly odd in places, requires some serious thinking out of the box, but immensely satisfying on completion.
Life is like a box of chocolates; often good, sometimes disappointing, occasionally orange flavoured.