HOW DID THE OUTAGE HAPPEN?

*Time synchronisation mechanisms across several nodes on Australia's east coast were not working properly about 4.30am, causing issues to calls and data across the network

* The root cause of the outage remained unknown but Telstra will investigate how and why it happened

* There is no evidence of malicious activity

WHO WAS IMPACTED?

* Thousands of Telstra customers were unable to make phone calls or access data 

* WA reported issues for citizens making triple-zero calls, forcing Telstra to conduct welfare checks on customers who could not get through

* All regional rail services were suspended in Victoria, while some NSW lines were also cancelled

* Canberra's public transport ticketing network MyWay+ went offline

* Commonwealth Bank have confirmed some EFTPOS terminals were not working and urged operators to swap to an Optus connection

* 378 traffic signals went offline in SA but remained in a fixed pattern

* Some customers were locked out of digital government services, unable to access verification requirements

WHAT ARE PEOPLE SAYING?

* "We've been able now to restore some of these nodes, but that will take time for that to reset across all the thousands of servers across the network"  - Telstra chief financial officer Michael Ackland

* "The Triple Zero custodian is in constant contact with Telstra (and) with emergency services ... Telstra have indicated to the government there's no evidence of it being malicious" - Prime Minister Anthony Albanese

* "There will almost certainly be valuable lessons for strengthening the resilience of critical transport infrastructure and better protecting passengers from similar disruptions in the future" - Swinburne transport expert Professor Hussein Dia

OTHER RECENT LARGE-SCALE OUTAGES

* Optus had a nationwide outage in September, and another in November. Two people who could not contact emergency services died in the September outage

* Vodafone had a national outage in June