An attack on the systems of British telco TalkTalk last October cost the company as much as £80 million (A$164 million) and 101,000 lost customers.

In the days following the attack chief executive Dido Harding warned the company's 4 million customers that their financial data had been put at risk.
The numbers affected turned out to be far fewer, with limited data stolen from about 157,000 people, but the bad publicity nevertheless caused a spike in defections.
"We saw a big dip inevitably in early November and then the business started returning to normal through December and very much back to normal now," Harding said today.
Five young men aged between 15 and 20 were arrested and freed pending further inquiries, police investigating the attack said last year.
A total of 101,000 customers left as a result of the breach, totalling less than 3 percent of the subscriber base, the telco revealed today.
Bigger rivals Sky and BT benefited from TalkTalk's problems, adding 144,000 and 130,000 broadband customers respectively in the last three months of 2015.
TalkTalk shares, which have fallen as much as 36 percent since October, were trading up more than 10 percent at 240.7 pence at 1035 GMT.
Analysts at Jefferies, who rate TalkTalk "underperform", said: "Bearing in mind the unprecedented bad publicity that the company faced and the need to withdraw from active marketing for a time, these results look less bad than could have been feared."
The financial costs included a one-off £40 million to £45 million charge, and a £15 million impact on trading in the third quarter to end-December. There would also be £20 million hit from the reduced customer base in its final quarter, the telco said.