The chip manufacturer has reassured that the attack was due to a "misoperation" when installing software for one of its new tools rather than a malicious attempt at the firm, leaving confidential information firmly secure.
"Certain factories returned to normal in a short period of time, and we expect the others will return to normal in one day", the company said in its Saturday statement. The impact on Apple's iPhone production schedule is also not known, although TSMC expects the incident "to cause shipment delays and additional costs".
The report quotes a Sanford C. Bernstein analyst who said in a research note on Monday that he thinks all of TSMC's 12-inch wafer fabrication plants had been infected.
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TSMC previously said about 10% of its revenues would be generated from its most-advanced 7nm process technology in the third quarter of 2018, and the proportion would reach 20% in the fourth quarter, with an over 20% in all of 2018.
Or it could simply be a bit of rogue code that's evolved from a bug in the system and has spread itself into TSMC's machines. The company didn't immediately respond to CNET's request for further comment.
Of course, Bloomberg was most interested in the possible consequences to the production of Apple iPhone chips.
The virus wasn't introduced by a hacker, TSMC told the publication, adding that the company had contained the problem and restarted some manufacturing, though some facilities won't be back up till Sunday. To the big questions concerning the financial impact of the virus attack, and the production impact, the TSMC representative was reticent to answer.