Wasn't the people that was with Anko when they watched the tape from the second chunin exam and Gaara had finished in a record time and they where commenting on it, ANBU? If i remember correctly one of them thought to himself "It would be impossible for me, no, for any chunnin to go threw the whole forest of death with out getting a signle scratch". That indicate to me that he was a chunin. But maybe it's just me remembering wrong. Gonna go look for those manga pages and see if it really was like that.

EDIT: Found it. http://www.onemanga.com/Naruto/58/05/ . Seems like that dude was not an ANBU.