Security researchers have uncovered new privacy threats that could allow every device operating on 3G networks to be tracked. Off-the-shelf equipment could be used to exploit the flaw, allowing the physical location of devices to be revealed. Researchers tested the attacks against network providers including T-Mobile, Vodafone and O2 in Germany, and French outfit SFR. Another vulnerability lay in the Authentication and Key Agreement protocol, which is used to provide authentication between a device and a network by providing secure shared session keys.
Source: https://thehackernews.com/2012/10/security-flaw-in-3g-could-allow-anyone.html