Jack Lin, who identified himself as the head of Cloaker, said in a phone interview in China that his company provides the back-end technology for thousands of apps but does not investigate its clients.
"We hope that our clients are all official sellers," he said. "If they are using these brands, we need some kind of authorization, then we will provide services."
Mr. Lin said Cloaker charged about 20,000 renminbi — about $3,000 — for an app written in English.
But like so many of the apps his company produces, Cloaker is not what it purports to be. Its website is filled with dubious claims, such as the location of its headquarters, which it says is at an address smack in the middle of Facebook's campus in Menlo Park, Calif.
In the interview, Mr. Lin at first said he had offices only in China and Japan. When asked about the California office, he then claimed to have "tens of employees" at the Facebook address.
China is by far the biggest source of fake apps, according to security experts.
Many of the fake retail apps have red flags signaling that they are not real, such as nonsensical menus written in butchered English, no reviews and no history of previous versions. In one fake New Balance app, for example, the tab for phone support did not list a phone number and said, "Our angents are available over the hone Monday-Firday."
Data from Apptopia show that some of the fake apps have been downloaded thousands of times, although it is unclear how many people have actually used them. Reviews posted on some of the apps indicated that at least some people tried them and became frustrated. "Would give zero stars if possible," wrote one reviewer of the fake Dollar Tree app. "Constantly gets stuck in menus and closes what you were doing and makes you start over."
Mr. Mason says consumers want to shop online and they search for apps from their favorite stores and brands.
"The retailers who are most exposed are the ones with no app at all," he said. Dollar Tree and Dillard's, for example, have no official iPhone apps, which made it easier to lure their customers to the fake apps.
But the counterfeiters have also mimicked companies that do have an official presence in the App Store, hoping to capitalize on consumer confusion about which ones are real.
The shoe retailer Foot Locker., for example, has three iPhone apps. But that did not stop an entity calling itself Footlocke Sports Co. Ltd. from offering 16 shoe and clothing apps in the App Store — including one purporting to be from a Foot Locker rival, Famous Footwear.
Similarly, the supermarket chain Kroger Company has 20 iPhone apps, reflecting the various retail chains in its empire. An entity calling itself The Kroger Inc. had 19 apps, purporting to sell things as diverse as an $80 pair of Asics sneakers and a $688 bottle of Dior perfume.
Some of the fake apps have even used Apple's new paid search ads to propel them to the top of the results screen when customers search for specific brands in the App Store.
Jon Clay, director of global threat communications for Trend Micro, an internet security firm, said Apple's tight control over the iPhone had historically kept malicious apps out of its App Store. Fake apps appeared more often on Google's Android platform or on third-party app stores, he said.
But that is beginning to change. Shortly after the Pokémon Go game was released in the United States in July, for example, a spate of fake iPhone apps related to the game appeared, especially in countries where the game was not yet available.
"The criminals are going to take advantage of whatever is hot," Mr. Clay said.
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