How to Cheat at VoIP Security
If VoIP engineering is not your specialty, this guide provides an introduction to VoIP security, and covers exploit tools and how they can be used against VoIP systems.
TABLE OF CONTENTS How to Cheat at VoIP Security
PSTN Protocol Security
If you thought that PSTN protocols are more secure than the IP protocols riding on PSTN access circuits, then prepare to be shocked. In some respects, one of the greatest threats to the Internet is the PSTN itself.
SS7 and Other ITU-T Signaling Security
Despite the fact that ITU-T signaling protocols prior to SS7 are notoriously insecure (see the sidebar on Blueboxing and the Phone Phreaking community earlier in the chapter), they continue to be deployed around the world along with older switching equipment that is vulnerable to toll fraud, eavesdropping, and other risks. If your VoIP system will be interfacing with such equipment, take countermeasures to reduce potential exposure and liability, set alarms, and review logs.
That is not to suggest that SS7 is particularly secure, but it is much harder for a subscriber to inject signaling into an SS7 network. That being said, the primary threat for SS7 networks are the peering arrangements (particularly among CLEC partners) for injection of false and/or fraudulent signaling and other messaging information. SS7 as currently defined does not have policy controls built in to address this issue. The risks and countermeasures were summarized quite well by the 3GPP SA WG3 Technical Specification Group in January 2000 for SGTR 33.900 V1 .2.0:
The security of the global SS7 network as a transport system for signaling messages e.g. authentication and supplementary services such as call forwarding is open to major compromise.
The problem with the current SS7 system is that...
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