Law-enforcement officials in the U.S. are expanding the use of tools routinely used by computer hackers to gather information on suspects, bringing the criminal wiretap into the cyber age.

Federal agencies have largely kept quiet about these capabilities, but court documents and interviews with people involved in the programs provide new details about the hacking tools, including spyware delivered to computers and phones through email or Web links—techniques more commonly associated with attacks by criminals.

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People familiar with the Federal Bureau of Investigation's programs say that the use of hacking tools under court orders has grown as agents seek to keep up with suspects who use new communications technology, including some types of online chat and encryption tools. The use of such communications, which can't be wiretapped like a phone, is called "going dark" among law enforcement.

A spokeswoman for the FBI declined to comment.

The FBI develops some hacking tools internally and purchases others from the private sector. With such technology, the bureau can remotely activate the microphones in phones running Google's Android software to record conversations, one former U.S. official said. It can do the same to microphones in laptops without the user knowing, the person said. Google declined to comment.

The bureau typically uses hacking in cases involving organized crime, child pornography or counterterrorism, a former U.S. official said. It is loath to use these tools when investigating hackers, out of fear the suspect will discover and publicize the technique, the person said.

The FBI has been developing hacking tools for more than a decade, but rarely discloses its techniques publicly in legal cases.

For more on the FBI's hacking toolkit, see The Wall Street Journal.