The government has confirmed 121 computer memory sticks have been lost or stolen in the past four years.
Five of them contained information classified as "secret".
The MOD said it had already taken action to ensure that data was better protected in future.
But Liberal Democrat MP Sarah Teather - who uncovered the information in a Parliamentary Question - said there was much we still did not know.
Bookmark with:
What are these?
E-mail this to a friend