The daily business briefing: February 25, 2016

1.

Apple engineers are working on security upgrades to make iPhones even harder — even "impossible" — to break into, The New York Times reported Wednesday. The changes involve methods like the ones federal investigators want help bypassing to access data on a locked iPhone used by one of the killers in the 2015 San Bernardino attack. The security upgrades could create a major new hurdle for law enforcement agencies even if the FBI wins its current court fight for an iPhone backdoor that Apple CEO Tim Cook says would be "the software equivalent to a cancer."

2.

Target reported Wednesday that its online sales had jumped by 34 percent in the last quarter, which included the critical holiday shopping season. Digital sales for the industry overall grew by 9 percent in November and December, according to the National Retail Federation, and Walmart gained just 8 percent online in the quarter. Target's gains signaled progress in its effort to establish itself as a powerful force in e-commerce, even though online sales remain just 5 percent of its total.

3.

Chinese stocks plunged by 6.4 percent on Thursday, intensifying worries about the state of the world's second largest economy. The turmoil came as China prepares to host the world's leading central bankers and finance ministers at a G-20 meeting starting Friday in Shanghai, where the Chinese government is expected to address fears over its falling markets. European stocks made gains despite China's troubles, clawing back after two days of losses as global markets fluctuate due to oil prices.

4.

The Islamic State has released a video containing vague threats against Twitter CEO Jack Dorsey and Facebook CEO Mark Zuckerberg over their companies' efforts to block terrorist content. Both companies in January sent representatives to the White House to discuss addressing terrorists' online activities. The video, which shows the faces of Dorsey and Zuckerberg with mock bullet holes over them, says terrorists have 10,000 Facebook accounts and 5,000 Twitter profiles. A Twitter spokesperson said the company had no response, because it gets threats "all the time."

5.

Walmart on Wednesday became the latest retailer to pull hoverboards from its website over concern for customer safety. The Consumer Product Safety Commission has called hoverboards unsafe because they "pose an unreasonable risk of fire." Amazon this week also quietly pulled the self-balancing scooters from its site, following similar moves by Target and Toys R Us. Several airlines, including Delta, United, JetBlue, and American, also have banned the trendy devices.