A group of 17 Internet companies, including Twitter, eBay, Airbnb and LinkedIn, submitted a joint court brief supporting Apple in the case in which the United States government is seeking Apple’s help to break into an iPhone used by a gunman in a terrorist attack in San Bernardino, Calif., last year. Separately, AT&T also filed a brief backing Apple.
In all, around 40 companies and organizations, including Google, Microsoft, Facebook, Yahoo, Snapchat and Dropbox, are expected to jointly submit court briefs later on Thursday. More than 40 people, including prominent security experts and academics, are also planning to sign on to briefs. Apple’s allies are set to submit about a dozen briefs this week.
The briefs address different facets of the case, focusing on free speech implications, the importance of encryption and concerns about government overreach, among other themes.
The group of companies that includes Twitter, LinkedIn and others challenged the government’s use of the All Writs Act, a statute from 1789, to force Apple to unlock the iPhone used by one of the San Bernardino assailants. AT&T also similarly objected to the use of the law.
The government, the group including Twitter and LinkedIn said in its filing, “seeks unbounded authority to compel Apple to design software that does not currently exist and that will circumvent and undermine security measures intended to protect its users’ data.”
The case became public last month, when a federal magistrate judge in California ordered Apple to bypass the security functions on the iPhone. Timothy D. Cook, Apple’s chief executive, opposed the order, and the company has argued that the case could have far-reaching implications for other devices and software.
Other tech companies were initially careful in their support of Apple. Last week, companies including Microsoft began to throw their weight behind Apple more forcefully, saying they planned to file briefs supporting Apple in court.
On Wednesday, a group of iPhone security and cryptography experts including Charlie Miller, Bruce Schneier and Jonathan Zdziarski, submitted a brief warning that any custom software Apple was forced to create to help authorities unlock the iPhone would be in high demand from authoritarian governments and hackers, to whom it would probably leak. They cautioned that the court order would set a precedent that could let authorities turn other devices with microphones — including Amazon’s Echo and Samsung television sets — into surveillance devices.
This week, Salihin Kondoker, the husband of one of the victims in the San Bernardino attack, also wrote a letter to the court siding with Apple, saying he thought that there was little valuable information on the iPhone, which the killer was issued by his employer. Mr. Kondoker, whose wife, Anies, was shot three times but survived the attack, said Apple’s fight was about something bigger than one phone.
“They are worried that this software the government wants them to use will be used against millions of other innocent people,” he wrote. “I share their fear.”