US mobile security startup Lookout built on the popularity among smartphone and tablet owners by offering its gadget-defending expertise to businesses.

Since the San Francisco-based startup launched in 2007, the number of people who have installed free Lookout malware-fighting applications on smartphones or tablets has climbed to about 40 million.

Lookout said its successful spread caught the attention of businesses grappling with ways to keep data and networks safe as lifestyles increasingly involve people using personal smartphones or tablets at work.

"The hope we had in 2007 was that if we built a great consumer product we would get pulled into the enterprise," Lookout chief technology officer Kevin Mahaffey told AFP.

"In the past year, thousands of companies have reached out to us."

Employees at more than half of Fortune 1000 companies use Lookout Mobile Security applications, according to the startup.

Challenges to keeping business safe include giving workers access to data or networks through smartphones or tablets while still allowing personal uses such as games or social networking, according to Mahaffey.

"It requires business IT departments to relax their historically iron fists on mobile security deployment," he said.

"People expect much more freedom on their mobile devices than on their company desktop (computers)."

Lookout's free applications tailored for iPhones, iPads, Kindles, and Android-powered devices expose malicious software, back up data, and let people trigger remote alarms in smartphones to locate misplaced devices.

Lookout is the top mobile security application for smartphones built on Google-backed Android software.

A premium version of Lookout, available for $30 a year or three dollars monthly, includes features such as backing up pictures and remotely locking and wiping data from smartphones that are lost or stolen.

Pricing wasn't disclosed for versions of Lookout tailored for businesses.

Mahaffey said that the broad Lookout user base is an asset because while defending smartphones and tablets the company gets valuable insights into tools and tactics used by hackers.

"We might have a user in China who will never pay us anything, but since our system gets smarter while protecting their phone it benefits our paying customers," Mahaffey said.

The kick-off of Lookout for Business came with the announcement that leading Android smartphone maker Samsung has enlisted the company to add a layer of defense to mobile devices tailored for businesses.

"Think of it as a secure vault for business apps or data on a device," Mahaffey said. "Lookout will be built into that."