We have proposed the CDMA-based fingerprinting scheme in IWSEC2007, and the detector is improved by reducing the interference among colluders' fingerprint signals in IH2008. In this study, we evaluate the false-positive detection when the number of colluders is more than 100, and show the bugs in the design of threshold for the determination of guilty. We fix the bugs and further improve the performance by adaptively calculating proper thresholds. Copyright © 2009 ACM.