Straight from Zodiac's post on the official forums to your screen:

Ladies and gentlemen, the third Korean closed beta has finally been announced on the Korean official website. It's been long since something happened but I'm sure the wait has been worth it[.]

The test will be held during 10 days, from 2/26(Friday) to 3/7(Sunday). The test will include a [whopping] 20,000 participants chosen from applications and people that have contributed greatly during discussions on the bulletin boards.

Want to read the original post? There you go.