In the latest instance of a Silicon Valley tech company being drawn into the shadowy activities of the National Security Agency, Apple on Tuesday denied any involvement in the spy agency's alleged efforts to hack into and monitor iPhones.

Responding to a report by Germany's Der Spiegel magazine this week that the NSA was able to use a program called "DROPOUT JEEP" to infiltrate a number of computing devices, including the iPhone, Apple has joined other tech giants like Google and Cisco in insisting it never worked with the agency and was unaware of efforts to target its products.

The Der Speigel report included a leaked NSA graphic from 2008 that laid out the program being developed, referring to it as a "software implant" that allows infiltrators to retrieve data from iPhones such as contact lists and to even turn on and use the device's microphone and camera.

It's unclear where Der Spiegel obtained the information, although the magazine has worked in the past with NSA leaker Edward Snowden.

The report comes at a sensitive time for Apple, which earlier this month announced a deal to sell iPhones on China Mobile's network, giving the Cupertino tech giant a significant presence in the world's largest mobile market. China Mobile has more than 700 million customers, and any suggestion that the iPhone could be vulnerable to U.S. government break-ins could present huge problems for Apple.

According to the leaked documents, shared publicly by Der Spiegel and security researcher Jacob Appelbaum, the NSA's program lets the agency do a wide range of things on someone's iPhone, including reading text messages and personal contacts.

The NSA, says the report, claims a 100 percent success rate when it comes to implanting iOS devices with spyware.

"Either (the NSA) have a huge collection of exploits that work against Apple products, meaning they are hoarding information about critical systems that American companies produce, and sabotaging them, or Apple sabotaged it themselves," Appelbaum said at the Chaos Communication Conference in Hamburg, Germany.

Apple vigorously denied any involvement, saying it "has never worked with the NSA to create a backdoor in any of our products, including iPhone."

Some news reports pointed out that the NSA graphic was dated, and said the information suggested that installation of malware to gain access to an iPhone could be done only if the NSA had possession of the phone.

The report said the NSA was working on a way to implant the software using a remote method, but it's unclear how much progress the agency has made on that front.

Apple said it will "continue to use our resources to stay ahead of malicious hackers and defend our customers from security attacks, regardless of who's behind them."

Analyst Carolina Milanesi with Kantar Worldpanel said that while she believes Apple's assertion that the company had no knowledge of the NSA's activities, the tech company now joins others caught up in the spy agency's shadows.