Federal officials say that StealthGenie violated the law by offering the ability to secretly monitor phone calls and other communications in almost real time, which is typically legal only for law enforcement officials. (Reuters)

Federal officials on Monday announced the arrest of the maker of a popular smartphone app marketed as a tool for catching cheating spouses by eavesdropping on their calls and tracking their locations — a technology critics have dubbed “stalker apps.”

In the first prosecution of its kind, federal officials said that StealthGenie violated the law by offering the ability to secretly monitor phone calls and other communications in almost real time, something typically legal only for law enforcement. The arrest comes as the market for surveillance software has grown so big that Web sites rank such apps on their price, features and even customer service.

Activists working to prevent domestic violence long have urged federal officials to take more aggressive action on the high-tech tools used by abusers. Although it is often advertised as a system for monitoring small children or suspicious employees, surveillance software frequently ends up in the hands of people who might beat their spouses or partners, activists say.

StealthGenie — with prices ranging from $100 to $200 a year for a “Platinum” version — allows buyers to track nearly any movement or utterance of their target, underscoring the remarkable surveillance capabilities of iPhones, BlackBerrys and Android devices.

“The fact that it’s running in surreptitious mode is what makes it so foul,” said Cindy Southworth of the National Network to End Domestic Violence. “They work really hard to make it totally secretive.”

The chief executive of the company that makes StealthGenie, Hammad Akbar, 31, of Lahore, Pakistan, was arrested in Los Angeles on Saturday, according to a news release from the Justice Department.

A grand jury in the Eastern District of Virginia indicted Akbar in August, and the case involves charges of conspiracy, sale of a surreptitious interception device and advertising a surreptitious interception device. That previously sealed indictment was announced Monday afternoon.

Court filings suggest that Akbar has contended that any legal issues were limited to the users of SmartGenie, not its maker. “When the customer buys the product, they assume all responsibility,” he wrote in a 2011 e-mail, court filings show. “We do not need to describe the legal issues.”

Efforts to reach Akbar’s attorney, based in Los Angeles, were not successful.

“Selling spyware is not just reprehensible, it’s a crime,” Assistant Attorney General Leslie R. Caldwell, head of the Justice Department’s Criminal Division, said Monday in the news release. “Apps like StealthGenie are expressly designed for use by stalkers and domestic abusers who want to know every detail of a victim’s personal life — all without the victim’s knowledge. The Criminal Division is committed to cracking down on those who seek to profit from technology designed and used to commit brazen invasions of individual privacy.”

The indictment, which could lead to others if the prosecution is successful, comes amid a swirling national and international debate over the appropriate uses of surveillance by governments and private individuals. A Washington Post poll last year found deep concern that governments and private companies had intruded too far into the lives of Americans, yet respondents said some degree of tracking of children and the elderly had become routine.

StealthGenie, like several other software surveillance programs on the market, requires that a user gain physical access to a targeted smartphone. Once StealthGenie is installed, it continuously reports information back to the user without the phone owner’s knowledge.

Almost anything on a smartphone is vulnerable to collection by StealthGenie, including texts, photos, calendar entries, contacts and Web browsing history. Calls can be recorded and listened to later, and the microphone can be activated so that the user can simply listen to the ambient sounds of a target’s daily life, according to a cached version of the company Web site, which was not active Monday. The app also plots the moment-by-moment movements of a target on an online map, and can send an alert to the user if the phone goes to selected locations.

Although tracking a person’s location without consent is illegal in most circumstances, the indictment focuses heavily on the marketing of StealthGenie’s ability to intercept calls and other communications, in alleged violation of the federal Wiretap Act. The indictment also reports that investigators found documents showing that Akbar’s company, InvoCode, based in the United Kingdom, estimated that 65 percent of purchasers of StealthGenie were likely to be people suspecting their romantic partners of infidelity.

“According to our market research[,] the majority chunk of the sales will come from people suspecting their partners to be cheating on them or just wanting to keep an eye on” their romantic partners, the indictment says.

It’s legal for parents to eavesdrop on their children if they are minors, and it would also be legal for a person to track or collect the communications of another adult who consents to the surveillance — as may be the case when adults set up systems to monitor elderly relatives who have medical issues.

A smartphone app, even one with powerfully intrusive technology, might pass legal muster if marketed for those purposes, legal experts say. A successful prosecution of the maker of StealthGenie or similar software would probably have to demonstrate that it is intended mainly for the monitoring of adults who do not know about or consent to the surveillance; court filings say the “vast majority” of those being monitored were adults and “many cases” involved suspected infidelity.

“You have to prove this business model, the whole business model, is ‘We’re helping you commit a crime,’ ” said Danielle Citron, a University of Maryland law professor. “That’s a hard sell.”

An effort this year by Sen. Al Franken (D-Minn.) to outlaw stalker apps has not been successful.

Akbar’s arrest marks the culmination of a three-year investigation. Court filings show that prosecutors were given a sealed, temporary restraining order on Friday that shut down his Web site before he was taken into custody Saturday at Los Angeles International Airport.

The investigation appears to have begun in November 2011, when an FBI agent browsing spyware applications came across the StealthGenie Web site. Other agents soon joined the probe — and were particularly troubled by the secretive nature of the app and the audience its makers apparently targeted.

“StealthGenie is a mobile spy software that can help you find out what your husband, wife, boyfriend or perhaps your girlfriend are hiding from you,” said one section of the Web site. “You can monitor them without getting suspected because once installed, StealthGenie is completely undetectable and operates mutely without interrupting the calls or other cellular functions.”

The StealthGenie app was also different from some of its competitors in that it would send users a text or e-mail when the person being monitored did certain things, court filings show.

An undercover agent purchased the app and others performed a technical analysis. Prosecutors wrote in court filings that as of December 2011, hundreds of people across the world had been monitored by the app, and they estimated that tens of thousands might have been in the years that followed.