When I looked for employment after leaving I looked at the UN. They have a number of jobs in 'information management' ranging from librarian to statistician. There is no central agency. A lot of the individual components have an investigation element: think war crimes based in the Hague, and WHO in Geneva looking at counterfeit medicines. Can't comment on the Hague, but WHO were tossers. Information is collected, collated, and analysis takes place (after a fashion). So, yes and no.
There is an ex op inter who did a crosspol tour at 13 sigs in the 90's who now works for the UN. Not quite sure what he does for them, but we swap emails now and then. If you want to be put in contact PM me your details and I'll pass them on.
Why should the UN need it's own Intelligence Service when there are so many others working in the building they could tap in to?
Not that the British would ever get involved in such activities ( please pardon the pun on "tap") I'm sure the current UN Director of Security would put a stop to any of those activities.
On deployments the UN does not allow the use of intelligence, rather they prefer "operational information".
Funny that so many correspondants with Jane's Intelligence Review seem to sign up 6 month mobilisations to work with the UN in information management roles. Quite handy that as members of the British Territorial Army that they still have their vetting as well.