Independent review finds Telstra failed to prioritise systems behind major network outage

Telstra did not prioritise systems that caused a major nationwide network failure and lacked the technical expertise to properly maintain them, an independent investigation has found.

The results of the review into the telco's 8 July network failure, which left thousands of Australians unable to make calls or access data, were released on Tuesday.

The outage sparked chaos with Triple Zero calls and businesses affected, along with failures across train networks and electronic payment services.

A lack of ownership and oversight of the functions that led to the outage were identified as key contributing factors by Technology Audit Partners in the report.

The outage began at 2.50am, nearly an hour earlier than identified by Telstra at the time.

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Following the outage, Telstra confirmed it had conducted welfare checks on those who tried to place more than 600 unsuccessful emergency calls.

The investigation also found a further eight Triple Zero calls did not go through to emergency services during the outage. Welfare checks were conducted in relation to those unsuccessful calls, with no adverse outcomes identified, according to the company.

The outage was triggered by a software update not being done on a GPS card, which resulted in incorrect date information.

It was primarily a result of Telstra not treating network timing as a critical capability, the report found.

On the night of the outage, the two primary engineers involved in the botched upgrade were on mandatory stand-down, the report found.

"The overarching finding is we did not prioritise our timing system inside our networks at the highest level as a critical capability, which is exactly what it should have been," chief executive Vicki Brady told media on Wednesday.

Brady said additional resources and expertise had been allocated to the impacted area.

Since the outage, just over 30,000 customers have contacted the telco, which has processed credits of just under $1 million for those customers.