According to Biham, the attack allows an eavesdropper to tap into a conversation while a call is been set up and a phone at the receiver's end is still ringing. After this, a conversation can be overheard.
“Using a special device it's possible to steal calls and impersonate callers in the middle of a call as it's happening,” Biham told Reuters.
The security loophole arises because of a fundamental mistake made by GSM developers in creating a system which corrected for interference of the line prior to encrypting a conversation, he explained.
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Both parties agree that the issue does not affect 3G phones, which use different protocols and security mechanisms than legacy GSM handsets. [Privacy Digest]