ANT has also developed bits of malware collectively referred to as "Persistence" that is designed to penetrate and install its payload in the BIOS of PCs, servers, and the firmware of routers or other networking equipment. Once installed, the payloads become part of the core operating code of the device in which they're implanted, and are reinstalled on motherboards or hard drives even after previous versions of the firmware and operating systems have been wiped and replaced, according to Der Spiegel, which got a look at the TAO catalog of attack devices courtesy of Snowden.
Specifics remain elusive
There is no information available on the specific techniques the NSA used to attack either the Huawei servers or source code. The catalog and many other reports released by Snowden were from the same period as the NSA's attacks on Huawei, making it likely the exploits and tactics used were similar to those in the Snowden documents.
It's not clear whether they were involved with the effort to bug Huawei source code, but the initial attacks on Huawei were launched after consultation with the White House intelligence coordinator and with cooperation from the FBI.
The NSA was hardly alone in worrying about digital espionage from China, or even suspicion about Huawei.
A 2008 report to Congress from the US Defense Department described significant increases in China's ability to attack servers belonging to Western governments and corporations, and a suddenly increasing will to do so.
Secret US State Department cables published by WikiLeaks in 2011 traced a series of cyberattacks code-named "Byzantine Hades" the cables said were launched by units of the Chinese People's Liberation Army (PLA) against Western government, university, and corporate servers beginning in 2006.
US-based investigators told Reuters at the time that Chinese hackers had stolen "terabytes" of sensitive data ranging from usernames and passwords to details of sophisticated weapons systems.
A history of suspicion
Huawei got plenty of attention as one of the fastest-growing networking companies in the world at the time, but was also highlighted as a possible security risk.
In 2008, prompted by Huawei's effort to break into the U.S. market by buying a stake in 3Com, the US Congress launched the first of what would be two separate in-depth investigations of Huawei. The investigation was dropped after Huawei backed out of the deal with 3Com.