Optus issues might result from the 2021 Facebook incident.

An Australian IT firm suggests a “configuration issue” as a likely cause for the nationwide disruption.

Experts suggest the prolonged Optus outage may be linked to the same issue that impacted Facebook two years ago. Cloudflare, an internet activity tracker, observed an increase in Border Gateway Protocol (BGP) announcements from Optus coinciding with the network’s downtime.

BGP functions as the internet’s navigation system, providing directions to specific destinations. According to Matt Tett, the managing director of Enex TestLab, while he couldn’t confirm the exact cause, it appears that at 4 am, Optus experienced a routing failure, leading to a noticeable surge in BGP announcements. Tett mentioned that upon waking up, he instinctively considered it either a cyber incident or a configuration problem, with configuration issues being the more common culprit in such significant problems.

Subscribe to Guardian Australia’s complimentary morning and afternoon email updates for your daily news summary.

He suggested that the company may have required dispatching an engineer to physically connect to one of the routers for resolution.

Optus is currently identifying responsibility, determining whether it involves an internal or external party,” he added, alluding to the potential involvement of a service provider partner.

Tett clarified that the reason for the extensive service disruption, impacting not only the internet but also landline and mobile services, is because modern networks are constructed on the Internet Protocol (IP). When an issue arises in the IP network, it can affect all their systems.

In a parallel incident, Facebook, WhatsApp, and Instagram were offline for five hours in 2021 due to a BGP-related problem. Facebook attributed it to a configuration change in the backbone routers managing network traffic between their data centers, leading to a cascading effect.

Addressing the global Facebook outage required a significant amount of time. Similarly, Kelly Bayer Rosmarin, CEO of Optus, informed the ABC that their engineers had attempted multiple restoration approaches to bring back mobile and internet services, but they had not yet achieved the desired results.

Following the widely publicized Optus data breach last year, exposing the personal details of 10 million customers, concerns naturally arose about the possibility of another cyber-attack. However, Bayer Rosmarin emphasized that a hack was “highly unlikely” as the cause of the outage, describing such incidents as “very, very rare.”

As one of Australia’s three major mobile network operators, Optus is keenly aware of the public’s reliance on its network and the need to take measures to ensure its uninterrupted operation. In its most recent annual report, Optus’s parent company, Singtel, mentioned that the company had implemented “essential network infrastructure diversity” to prevent disruptions and downtime.