Apple's biggest business rivals will be supporting the company in its court battle against the FBI.

Amazon (AMZN), Facebook, Google (GOOGL), Microsoft and other tech companies will file letters to the court stating that they stand with Apple, according to the companies and sources familiar with their plans.

Each has to file its brief to the court by March 3.

Microsoft (MSFT) was the first to say it would add its voice to the court battle. At a House Judiciary Committee hearing, Microsoft Chief Legal Officer Brad Smith said Microsoft believes Apple is right that the courts should not force it to write code that would help the FBI unlock a San Bernardino shooter's iPhone.

Smith said that Congress, instead, should draft updated laws that address how technology companies should work with law enforcement when a suspect's data was encrypted.

"I believe that Apple is making an important point," Smith said. "We agree wholeheartedly with Apple that the right place to bring this discussion is here, to the House of Representatives and the Senate so the people who are elected by the people can make these decisions."

Related: Apple tells court the government can't force it to write code

At the hearing, Smith showed off a prop: a century-old adding machine that he claimed was the most advanced technology from the time the All Writs Act was last updated. The All Writs Act is a central law that a magistrate-judge referenced in her order to Apple (AAPL).

"Put simply, we do not believe that courts should seek to resolve issues of 21st century technology with law that was written in the era of the adding machine," Smith said. "We need 21st-century laws that address 21st-century technology issues. And we need these laws to be written by Congress."

When a congressman congratulated Smith on his impressive prop, Smith noted, "It's amazing what you can buy on the Internet."