The ransomware, which only infects systems running Microsoft's Windows operating system, hit a number of Taiwan Semiconductor Manufacturing Co's fabrication plants on 3 August, it said, with the degree of infection varying from plant to plant.
WannaCry hit countless systems worldwide on 12 June 2017, with computers in Britain's National Health System among those affected. The ransomware used an NSA-built exploit that had been leaked on the Web in April that year.
In a statement, TSMC said it had contained the problem and found a solution. As of 2pm on 5 August (4pm AEST Sunday), it said about 80% of the tools affected by the ransomware had been recovered.
All it takes is lack of patching + vendor brings in infected laptop = bad weekend.— kevin (@GossiTheDog) 6 August 2018
"This virus outbreak occurred due to misoperation during the software installation process for a new tool, which caused a virus to spread once the tool was connected to the company’s computer network," Lora Ho, senior vice-president, chief financial officer and spokesperson, said.
"Data integrity and confidential information was not compromised. TSMC has taken actions to close this security gap and further strengthen security measures."
"We estimate the impact to third-quarter revenue to be about 3%, and impact to gross margin to be about one percentage point,"
"The company is confident that shipments delayed in the third quarter will be recovered in the fourth quarter 2018, and maintains its forecast of high single-digit revenue growth for 2018 in US dollars given on 19 July."
Bloomberg quoted Nehal Chokshi, an analyst with Maxim Group, as saying that delays to Apple should be limited as it appeared there had been no effect on wafers, the raw material for processors.
"My suspicion is that there will be minimal impact on Apple,” he said. “Nothing has been scrapped, just simply production days have been impacted."
Chokshi said the time taken to turn raw wafers into processors was about six to eight weeks and if that line of production was affected, then there would be longer delays. But in this case, the delay would just be the three days during which TSMC shut down production.
"This is really minor," he said. "I don’t think there’s a need to panic from Apple’s perspective or from an investor’s perspective."