An anonymous reader writes: Kim Zetter from WIRED writes an intriguing report about a vulnerability at the heart of our cell phone networks. It centers around Signaling System No. 7 (SS7), which refers to a data network -- and the protocols or rules that govern how information gets exchanged over it. Zetter writes, "It was designed in the 1970s to track and connect landline calls across different carrier networks, but is now commonly used to calculate cellular billing and send text messages, in addition to routing mobile and landline calls between carriers and regional switching centers. SS7 is part of the telecommunications backbone but is not the network your voice calls go through; it's a separate administrative network with a different function." According to WIRED, the problem is that SS7 is based on trust -- any request a telecom receives is considered legitimate. In addition to telecoms, government agencies, commercial companies and criminal groups can gain access to the network. Most attacks can be defended with readily available technologies, but more involved attacks take longer to defend against. T-Mobile and ATT have vulnerabilities with fixes that have yet to be implemented for example.