The security of next-generation 5G networks has dominated this year's Mobile World Congress in Barcelona, with conflicting views on the risks of moving to the new technology being debated on stage and in backroom meetings.
5G promises super-fast connections which evangelists say will transform the way we live our lives, enabling everything from self-driving cars to augmented-reality glasses and downloading a feature-length film to your phone in seconds.
But there are also security concerns, some of which have fuelled a drive by the United States and others to remove Chinese-made equipment from Western networks.
The concerns can be broken down into three main areas:
As 5G becomes embedded in everything from hospitals to transport systems and power plants it will rapidly become a part of each country's critical national infrastructure.
This makes the consequences of the networks failing or being deliberately sabotaged in a cyber attack significantly more serious.
"What makes people concerned is that you are not going to use 5G only for smartphones and consumers, you will connect, over time, infrastructure that is at the very core of our societies," said Thomas Noren, head of 5G commercialisation business area networks at equipment maker Ericsson.
Ericsson, Huawei and Nokia are the world's leading suppliers of telecoms equipment.
As 5G makes high-speed internet increasingly available, the number of devices in the network will increase dramatically.
These will include traditional mobile and broadband connections, but also internet-enabled devices from dishwashers through to advanced medical equipment. Industry association GSMA forecasts the number of internet-enabled devices will triple to 25 billion by 2025.
The larger the network, the more opportunities there are for hackers to attack, meaning there is an increasingly complex system with more parts that need protecting.
"Once you have complexity across a broader system, regardless of what it is, the complexity itself is a vulnerability," said Gee Rittenhouse, senior vice president for security at networking gear maker Cisco.
"You don't have a coherent view through the system, and once you don't have that coherent view there are gaps, and the adversaries... take advantage of those gaps, which open up security holes."
One of 5G's biggest changes is the ability to take the advanced computing power usually kept in the protected "core" of a network and distribute it to other parts of the system.
This will provide more reliable high-speed connections, and also means that future technologies such as augmented-reality glasses will not need inbuilt computing power because they can pull it from the network instead.
But it also means engineers will no longer be able to clearly segregate the sensitive and less-restricted parts of the system.
"It is going to fundamentally change the architecture of the network," Nokia CEO Rajeev Suri told Reuters.
The United States and others have warned that this means equipment made by Chinese companies such as Huawei Technologies, which Washington has accused of spying for Beijing, will have access to protected information.
Huawei has denied the allegations.