<title>Characterization of attacks on public telephone networks</title>

Abstract

The U.S. Public Telephone Network (PTN) is a massively connected distributed information system, much like the Internet. PTN signaling, transmission and operations functions must be protected from physical and cyber attacks to ensure the reliable delivery of telecommunications services. The increasing convergence of PTNs with wireless communications systems, computer networks and the Internet itself poses serious threats to our nation's telecommunications infrastructure. Legacy technologies and advanced services encumber well-known and as of yet undiscovered vulnerabilities that render them susceptible to cyber attacks. This paper presents a taxonomy of cyber attacks on PTNs in converged environments that synthesizes exploits in computer and communications network domains. The taxonomy provides an opportunity for the systematic exploration of mitigative and preventive strategies, as well as for the identification and classification of emerging threats.

Public Telephone Network Vulnerabilities

“…The replacement of in-band signaling with out-of-band (SS7) signaling largely eliminated the well-known colored box attacks [1,7,10,19]. However, the SS7 architecture and protocol are vulnerable because they possess limited authentication mechanisms (SS7 was originally designed for a closed community) [17,18,19].…”

“…However, private branch exchanges (PBXs) used by large enterprises commonly rely on in..;band signaling, and are therefore vulnerable to colored box attacks [10]. Moreover, certain advanced services engage in-band signaling [2].…”

“…PBXs often use legacy technologies (in-band signaling) which are known to have serious vulnerabilities (colored box attacks [7,10,19]; attack point 8). Indeed, PBXs -because they use many connections to the PTN backbone -are often used as bounce points for attacks [17].…”

“…Increased PTN access, coupled with Internet-PTN convergence (e.g., xDSL, Dial-Up and ISDN connections) [8,23], make it easier for attackers to enter and then exploit poody secured SS7 networks [10].…”

“…Wireless communications are inherently vulnerable. Moreover, the rapid evolution of wireless technologies, the lack of standards and the pervasive use of legacy systems give attackers opportunities to wreak havoc on a massive scale [10,19,22].…”