SAN FRANCISCO  - A slew of tech industry groups and civil liberties advocates are filing legal arguments backing Apple in its fight with the FBI, including security experts worried about hacking and independent app-makers who fear more burdens on their business.

These "friends of the court" briefs aim to bolster Apple's challenge of a court order that would force it to help FBI agents hack an encrypted iPhone used by a San Bernardino mass shooter. The government must file its response next week, before a hearing on March 22.

Among those backing Apple are some of its biggest competitors, including Google, Microsoft and Facebook, which have signaled they'll file a joint brief on Apple's behalf. A group of 17 smaller tech firms, including Twitter, LinkedIn, Airbnb and Reddit submitted a separate joint filing.