A software defect in a Telstra GPS node reset the network's internal clock to November 2006, triggering a nationwide outage that left customers unable to make calls, including to emergency services, and disrupted train communications across Australia.
What Happened
Telstra's chief financial officer, Michael Ackland, explained that the defect struck the company's GPS node, which provides precise time to the network's systems. The reset changed the time and synchronisation, which then propagated to the rest of the network, dialling back the internal clock to 2006.
This time error caused a 'digital domino chain,' as described by Khurram Shahzad, a senior analyst at Gartner. Network nodes, such as cell towers, authenticate their identity with the central data hub using security certificates that have strict validity windows. When the central time servers broadcast the wrong time, core network switches saw valid certificates as expired or invalid, assuming a security threat and terminating connections. This locked devices out of the network, throwing phones into 'SOS only' mode.
Impact on Emergency Services
Some customers attempting to dial triple zero could not be connected, despite failsafe systems that should have routed them to other mobile networks. Telstra has yet to explain why this handover failed but said the issue was resolved by Thursday. As of 1pm AEST on Thursday, 639 welfare checks were completed on people who made unsuccessful triple zero calls. Of those, 230 did not need assistance, 402 required follow-up, 170 were referred to police, and seven to emergency services.
Train Services Disrupted
The Australia Rail Track Corporation (ARTC) suspended services after the outage disrupted the national train communications system, which uses Telstra's 4G network for drivers to communicate with control centres. The chief executive of V/Line, William Tieppo, said Telstra's 4G network interfered with the satellite backup system used by train drivers. Overnight, Telstra repaired the network to ensure the 4G train radio system integrated correctly with satellite phones.
Ackland said Telstra was working with all affected businesses, including a small number of enterprise customers with residual impacts.
Telstra's Response
Ackland rejected comparisons to the Y2K bug, describing the incident as a software glitch. He said Telstra would conduct a root cause analysis with vendors, partners, and external support. Asked if the outage showed the network was fragile, Ackland said it was not, calling it a complex but robust system with redundancy, and called the incident unfortunate.
