I have spent an entire day trying to break into a Ninjastik and I have finally an answer to the question “how secure is a Ninjastik”. According to Ninjastik, it is definitely impossible to break into one and steal the data so today, I tried with my Thinkpad. After a long time of toying around with windows, I accidentally corrupted one of my disks which makes it now impossible to get any info out.
Note, never accidentally press the format button and also do not toy around with a Ninjastik. A day of trying and it got me no where.