Personal SMS messages of Telstra customers were sent to random recipients on competing networks across Australia on Thursday afternoon in a huge potential security breach for the telco.
Unwitting phone users across Australia took to Twitter to express confusion about receiving random SMS messages from about 3pm.
"I could have broken this guy's deal wide open," said Twitter user @IggyBusby, on receiving details of someone's business strategy that included the phrases "hold off on the" and "still in discussions with".
Other users received similarly perplexing messages.
Many online services rely on SMS messaging to deliver critical confidential information such as new pin numbers and links for resetting passwords, including banking and email services.
Thirty per cent of customers were affected, Telstra chief executive Andy Penn said.
Telstra shut down its text messaging service when it realised SMS messages were being misdirected. Investigations into how the privacy breach occurred were ongoing, Mr Penn said.
The glitch occurred after a fire broke out at the Chatswood Exchange in Sydney some time after midday, damaging power equipment.
"There's not much we can do about a fire occurring," Mr Penn said.
The outage map on the site indicated that all states and territories were affected.
Businesses were also affected by the outage, including Jetstar and Circus Royale.
Telstra customers took to Twitter and websites from 1.11pm to express their grievances over outages, which included mobile, landline and internet services.
In an unrelated incident, the official website for the Australian Taxation Office crashed on Thursday morning.
At 3.09pm, Telstra announced services were beginning to return to normal.
Services are beginning to restore. Thanks for your patience.— Telstra (@Telstra) February 2, 2017
About 3.25pm, Jetstar announced its systems were back online after manual check-in was used at several airports during the outage.
The incident follows a fire last year at another exchange in Brunswick, Melbourne, caused by faulty wiring.
While customers were offered compensation in the form of "free data days" after last year's incident, Mr Penn said there were no plans to offer compensation to customers after Thursday's outage.
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With Broede Carmody