Hydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose and cellotetraose, releasing cellobiose from the non-reducing ends of the chains. Belongs to the glycosyl hydrolase 7 (cellulase C) family. This protein, although sequenced from the genome of strain 74-OR23-1A, has only limited sequence identity to the corresponding protein produced by the locus NCU07340 determined in the complete genome sequence of Neurospora crassa 74-OR23-1A, due to extensive nucleotide sequence discrepancies mostly in the N-terminus.