Departmental Papers (CIS)

Date of this Version

November 2005

Document Type

Journal Article


Copyright 2005 IEEE. Reprinted from IEEE Security & Privacy, Volume 3, Issue 6, November-December 2005, pages 13-25.

This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the University of Pennsylvania's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to By choosing to view this document, you agree to all provisions of the copyright laws protecting it.


Many law enforcement wiretap systems are vulnerable to simple, unilateral countermeasures that exploit the unprotected in-band signals passed between the telephone network and the collection system. This article describes the problem as well as some remedies and workarounds.



Date Posted: 03 March 2006

This document has been peer reviewed.