DIS stands for Defence Intelligence Staff and is part of the MOD - Ministry of Defence.
The people who work for the DIS analyse information, unlike MI5, MI6 and GCHQ who gather it.
They work out what other countries' weapons can do. They had a very important role to play in deciding how dangerous Iraq's weapons were and the scientist Dr David Kelly would have worked closely with the DIS.
The Defence Secretary is in charge of the DIS.