Revelations about the National Security Agency (NSA) keep on coming, this time in the form of information about its elite hacking unit called Tailored Access Operations (TAO), which helps the agency target specific people and computer networks around the world and has the ability to install "backdoors" in computers and other devices in order to gain access to those networks.

The report, based on leaked documents from former NSA contractor Edward Snowden, was published on Sunday in the German magazine Der Spiegel.

The report shows that American spies intercept computer deliveries, exploit hardware vulnerabilities and even hijack Microsoft's internal error-reporting system to spy on their targets.

Citing internal NSA documents, the magazine said Sunday that TAO's mission was "getting the ungettable," and quoted an unnamed intelligence official as saying that TAO had gathered "some of the most significant intelligence our country has ever seen."

Der Spiegel said TAO had a catalog of high-tech gadgets for particularly hard-to-crack cases, including computer monitor cables specially modified to record what is being typed across the screen, USB sticks secretly fitted with radio transmitters to broadcast stolen data over the airwaves and fake cell phone base stations intended to intercept mobile phone signals on the go.

The unit, which is based out of San Antonio is able exploit weaknesses in the architecture of the Internet to deliver malicious software to specific computers, according to the report. Some agents at TAO are tasked with taking advantage of weaknesses in hardware or software distributed by some of the world's leading information technology companies, including Cisco Systems, Inc. and China's Huawei Technologies Ltd., the magazine reported.

Der Spiegel cited a 2008 mail order catalog-style list of vulnerabilities that NSA spies could exploit from companies such as Irvine, Calif.,-based Western Digital Corp. or Round Rock, Texas-based Dell Inc.

This appears to be the first revelation about the NSA that also details their exploits beyond the virtual world.

Der Spiegel said that if the NSA tracked a target ordering a new computer or other electronic accessories, TAO could tap its allies in the FBI and the CIA, intercept the hardware in transit and take it to a secret workshop where it could be discreetly fitted with espionage software or hardware before being sent on its way.

Intercepting computer equipment in such a way is among the NSA's "most productive operations" and has helped harvest intelligence from around the world, one document cited by Der Spiegel stated.

The targets of the sophisticated hacks ranged from suspected terrorists to world leaders. The NSA was able to read the Blackberry messages and emails of leaders around the world, according to the report.

According to Der Spiegel, the documents also show that the NSA would spy by exploiting Microsoft's crash reports, familiar to many users of the Windows operating system (the little dialogue box that pops up when a program freezes). The reporting system is intended to help Microsoft engineers improve their products and fix bugs, but Der Spiegel said the NSA was also sifting through the reports to help spies break into machines running Windows. One NSA document cited by the magazine appeared to poke fun at Microsoft's expense, replacing the software giant's standard error report message with the words: "This information may be intercepted by a foreign sigint (signals intelligence) system to gather detailed information and better exploit your machine."

Microsoft did not immediately return a call from The Associated Press seeking comment, but the company is one of several U.S. firms that have demanded more transparency from the NSA — and worked to bolster their security — in the wake of Snowden's revelations, whose disclosures have ignited an international debate over privacy and surveillance.

The Der Spiegel report caps off a week of attention around the NSA leaks. On Friday, journalist and Snowden supporter Glenn Greenwald chastised media for not being more critical of the government.

Also last week, a judge ruled the NSA's phone data collection program constitutional, and Snowden gave a lengthy interview to the Washington Post.

Al Jazeera and wire services