Ben Lovejoy, writing for 9to5Mac: We reported back in October on an iOS exploit that caused iPhones to repeatedly dial 911 without user intervention. It was said then that the volume of calls meant one 911 center was in 'immediate danger' of losing service, while two other centers had been at risk -- but a full investigation has now concluded that the incident was much more serious than it appeared at the time. It was initially thought that a few hundred calls were generated in a short time, but investigators now believe that one tweeted link that activated the exploit was clicked on 117,502 times, each click triggering a 911 call. The WSJ reports that law-enforcement officials and 911 experts fear that a targeted attack using the same technique could prove devastating. Of the 6,500 911 call centers nationwide, just 420 are believed to have implemented a cybersecurity program designed to protect them from this kind of attack.