Researchers have demonstrated an alarmingly simple technique for eavesdropping on individual GSM mobile calls without the need to use expensive, specialised equipment. Researchers have demonstrated an alarmingly simple technique for eavesdropping on individual GSM mobile calls without the need to use expensive, specialised equipment.During a session at the Chaos Computer Club Congress (CCC) in Berlin, Karsten Nohl and Sylvain Munaut used cheap Motorola handsets running a replacement firmware based on open source code to intercept data coming from a network base station.Armed with this, they were able to locate the unique ID for any phone using this base, breaking the encryption keys with a rainbow table lookup.Although far from trivial as hacks go, the new break does lower the bar considerably compared to previous hacks shown by the same reasearchers. In 2009, Nohl published a method for cracking open GSM’s A5/1 encryption design using a lookup table in near real time. What was missing, however, was a way of identifying the call stream for an individual phone in order to apply the lookup to a real call within the clutter of data moving back and forth between a particular base station and the many phones using it. That is what Nohl appears to have worked out in his latest demo.Another important detail is that Nohl was able to replace the firmware of the handsets with custom software. According to the BBC report on which most stories are being based, this was only possible because the Motorola handsets in question had been reverse engineered after an unspecified leak. How easy would it be to exploit the new hack? In short, not particularly easy. Creating a custom lookup table similar to Nohl’s would take months of work and any eavesdropper would still need to break into the handset in question.The crack does lower the bar from being a hardware problem to one of software expertise, which will cause some alarm in the GSM engineering community.Governments and the military won’t worry unduly as they will be using encrypted satellite phone systems and GSM phones equipped with extra layers of call encryption to make sensitive calls. Large companies might want to take note, however. Related content feature Top cybersecurity M&A deals for 2023 Fears of recession, rising interest rates, mass tech layoffs, and conservative spending trends are likely to make dealmakers cautious, but an ever-increasing need to defend against bigger and faster attacks will likely keep M&A activity steady in By CSO Staff Sep 22, 2023 24 mins Mergers and Acquisitions Mergers and Acquisitions Mergers and Acquisitions brandpost Unmasking ransomware threat clusters: Why it matters to defenders Similar patterns of behavior among ransomware treat groups can help security teams better understand and prepare for attacks By Joan Goodchild Sep 21, 2023 3 mins Cybercrime news analysis China’s offensive cyber operations support “soft power” agenda in Africa Researchers track Chinese cyber espionage intrusions targeting African industrial sectors. By Michael Hill Sep 21, 2023 5 mins Advanced Persistent Threats Cyberattacks Critical Infrastructure brandpost Proactive OT security requires visibility + prevention You cannot protect your operation by simply watching and waiting. It is essential to have a defense-in-depth approach. By Austen Byers Sep 21, 2023 4 mins Security Podcasts Videos Resources Events SUBSCRIBE TO OUR NEWSLETTER From our editors straight to your inbox Get started by entering your email address below. Please enter a valid email address Subscribe