Clone Wars Roil App World

In the fast-paced mobile-apps business, creating a hit app is no guarantee of success: Developers must also fend off the copycats.

App makers say a growing group of "cloners" are mimicking their products or misappropriating their names and images to ride an original app's success. The copycats often target top-selling apps and seek to siphon off users and potential revenue. Others carry malicious software. Despite their proliferation, app stores run by Google and others have been unable to weed them out.