The FBI has shut down a website that was allegedly selling a ‘stalker’ app designed to grant users access to someone else’s smartphone, turning the device’s microphone into a bug.

Hammad Akbar, 31, StealthGenie's CEO, was arrested in Los Angeles by US authorities on Saturday for distributing the undetectable app.

StealthGenie could intercept all incoming and outgoing calls on a mobile phone, according to the indictment. The app also granted absolute access to phone data, and all types of conversation could be monitored so long as the StealthGenie was within 15 feet of the device.

The website, which said it had more than 100,000 “satisfied customers,” charged £37 for the app before it was shut down by the FBI.

Assistant director of the Washington Field Office Andrew McCabe said: “This application allegedly equips potential stalkers and criminals with a means to invade an individual’s confidential communications.

“They do this not by breaking into their homes or offices, but by physically installing spyware on unwitting victims’ phones and illegally tracking an individual’s every move.”

The FBI said the it only would only take a couple of minutes access to the device to install the software. It worked on Apple, Android and Blackberry handsets.

The FBI said: “StealthGenie’s capabilities included recording and intercepting calls and monitoring e-mails, text messages, voicemails, photos, videos, and calendar appointments.

“The software could also activate a victim’s phone to eavesdrop on conversations within a 15-foot radius. All the communications could be viewed on a web-based dashboard.”

The app was developed by InvoCode Pvt Ltd which is based in Lahore, Pakistan, where Mr Akbar originally comes from, but the company had another HQ in Virginia.

The FBI obtained a court order on September 26 to take the service off-line, albeit temporarily while the investigation continues.

StealthGenie could be installed with just a couple minutes access to the victim's phone

The FBI said: “This is the first-ever criminal case concerning the advertisement and sale of a mobile device spyware app. Marketing for the app targeted people suspicious that their spouses or romantic partners might be cheating on them.”

The indictment states that Akbar and his co-conspirators allegedly programmed StealthGenie to sync all the data from the victim's phone with their customer's account – allowing them access to the handset via the web.

Prosecutors allege: “To install the app, a purchaser needed to obtain physical control over the phone to be monitored for only a few minutes.

The purchaser could then review communications intercepted from the monitored phone without ever again having physical control over the phone. Akbar and others alleged designed SteathGenie to be undetectable to users of the phone.”

The indictment claims that the app was designed for suspicious husbands or wives who suspected their partners of cheating or “if they just want to monitor them”.