The daily business briefing: April 5, 2018

Facebook said Wednesday that it now believes that the data-mining firm Cambridge Analytica improperly accessed the data of 87 million users — 72 million of them Americans — rather than the 50 million previously reported. The new estimate, revealed in a Facebook blog post on its plans to protect user data, threatened to increase concerns over the social network's handling of private data. Facebook also said that "malicious actors" had exploited search tools to collect the identities and other information on most of the social network's 2 billion users worldwide. The company already has apologized publicly for the Cambridge Analytica case, and Facebook CEO Mark Zuckerberg is scheduled to testify about the matter next week before the House Energy and Commerce Committee.

U.S. stocks fluctuated wildly on Wednesday as China and the U.S. announced tit-for-tat tariffs, escalating trade tensions between the world's two biggest economies. The Dow Jones Industrial Average plunged by nearly 2 percent in early trading before recovering and closing up by just under 1 percent. U.S. stock futures rose slightly early Thursday, suggesting the late rally could continue at the start of trading. The volatility came after China announced tariffs on $50 billion worth of U.S. goods just hours after the U.S. announced new taxes on imports of $50 billion worth of Chinese electronics and other goods. President Trump insisted in tweets that "we are not in a trade war with China" but "when you're already $500 Billion DOWN, you can't lose!"

The decline in Germany's diesel-car sales sped up in March, falling by a quarter after a court ruled that cities with air pollution problems could ban the vehicles, German automotive watchdog KBA reported Wednesday. Sales of diesel-powered vehicles fell by 17.6 percent in January and by 19.5 percent in February. Germany, Europe's largest auto market, is at the heart of the global backlash against diesel cars that was set off by German automaker Volkswagen's 2015 admission that it cheated in U.S. exhaust tests. "For the time being, new diesel sales will not recover," said Peter Fuss, a senior partner and automotive specialist in consultancy EY's German practice.

More than 3,100 Google employees have signed a letter urging Google to drop out of a Pentagon program using artificial intelligence to interpret video images. The technology could be used to improve drone-strike targeting, allowing for the identification of human targets but also potentially helping to avoid civilians. "We believe that Google should not be in the business of war," the letter to Google CEO Sundar Pichai says. The employees call for Google to quit the Pentagon's Project Maven and commit not to "ever build warfare technology." Google, which competes with Microsoft and Amazon for high-tech Pentagon work, said its contribution to Project Maven is "non-offensive," and both Google and the Pentagon said the work will not create an autonomous weapon that could fire without a human operator.

South Korean authorities on Thursday detained four executives from two South Korean cryptocurrency exchanges for questioning on suspected embezzlement. "They are being questioned about the embezzlement of billions of won from their clients' accounts and transferring it to their own," a prosecutors' office official told Reuters. Among the suspects detained was Kim Ik-hwan, CEO of Coinnest, the country's fifth largest cryptocurrency exchange. The others were not identified. Authorities in South Korea, the world's third largest cryptocurrency market, are working on tough regulations on cryptocurrency trading after vowing to crack down on what authorities have described as illegal and unfair practices.