Huawei is one of the world's biggest mobile phone makers. It's also at the centre of a row over cyber-security and the next-generation 5G phone networks being built. The UK government has decided to allow the Chinese tech giant to be part of its 5G network - but with restrictions. What is Huawei? Huawei was founded in 1987 in Shenzhen, southern China, by Ren Zhengfei, a former army officer. It started making communications equipment for mobile phone networks and is now a global leader, employing 180,000 workers. Huawei is the world's second-largest smartphone supplier after Samsung, with 18% of the market - ahead of Apple and others. Which countries are concerned about Huawei? At the heart of the debate is a simple question: can the West trust Huawei or will using its equipment leave communication networks, and our own mobile phones, vulnerable? The US says Huawei could be used by China for spying, via its 5G equipment. It points to Mr Ren's military background and Huawei's role in comms networks to argue it represents a security risk. Mr Ren was member of China's army, the People's Liberation Army, for nine years until 1983. He is also a member of China's Communist party. But Huawei says this is not relevant: "When Ren Zhengfei was a young man, you needed to be a CPC member to have any position of responsibility." Washington has banned US firms from doing business with Huawei, and wants its allies to ban it from their 5G networks. Australia and New Zealand have joined the US. Germany has put off making a decision - at least until the next EU summit in March. For the UK, using Huawei equipment may hit vital UK-US trade talks. The US has warned it could risk future security co-operation. But if the UK had banned Huawei from 5G, it could have faced Chinese retaliation.