[Original writeup](http://quangntenemy.blogspot.com/2014/03/ructf-quals-2014.html)
This is an easy GIF stegano, but it took me quite a while analysing the image until I noticed it contained 8 similar frames which wasn't easy to notice in GIMP by default (note to myself: next time check the frames first). It is common sense to combine them and find the differences. The positions of the different pixels are as marked below:
![task.png](http://3.bp.blogspot.com/-O-2VfIcQMWM/Ux3SNXE2iqI/AAAAAAAAAHs/vZRzZwiYSIw/s1600/task.png)
It isn't very straightforward, but the flag is hidden here in binary representation. Using black pixels as 0s and green pixels as 1s give you the flag: `RUCTF_e4dd9f5cee307b322c3a27abe66e3df9`