Journalist Glenn Greenwald underlines interest of National Security Agency in planting backdoors in U.S. suppliers’ routers and other networking devices in order to carry out its massive surveillance program. US government is always prohibiting the purchase of Huawei products due to suspected backdoors from the Chinese government, however the US government does the same thing with US suppliers’ hardware and repackages them with a factory seal before supplying them to overseas nations. The NSA thus gains access to entire networks and all their users.
Source: https://thehackernews.com/2014/05/nsa-reportedly-intercepts-us-made.html