The UK and its Five Eyes allies have issued a cyber attack warning over a China-backed "botnet" of more than 260,000 compromised devices.
Businesses have been urged by the National Cyber Security Centre (NCSC) and its allies in the US, Canada, Australia, and New Zealand to protect their devices from possible attacks.
It says a company based in China, with links to the country's government, has created and wields a botnet of more than 260,000 compromised devices around the globe.
Botnets are large networks of internet-connected devices that have been infected with malware.
As a result, they can be controlled by the group and used to carry out malicious attacks without the owners' knowledge.
Most commonly, they are used to carry out distributed denial of service (DDoS) attacks, which flood a website with traffic with the aim of knocking it offline.
But they can also be used to deliver malware.
Compromised devices can include routers, webcams, and CCTV cameras - among other internet-connected devices.
Around half of the company's devices, 126,000, were said to be in the US, with around 8,500 "nodes" in the UK.
Firms were urged to check if the security of their devices was adequate, noting that this botnet poses a particular threat to older equipment and devices whose security is not up to date.
Read more from Sky News:
Lebanon rocked by second wave of blasts
New 'grumpy' fish species discovered
Italia 90 star dies
Paul Chichester, NCSC director of operations, said: "Botnet operations represent a significant threat to the UK by exploiting vulnerabilities in everyday internet-connected devices with the potential to carry out large-scale cyber attacks.
"Whilst the majority of botnets are used to conduct coordinated DDoS attacks, we know that some also have the ability to steal sensitive information."
Follow Sky News on WhatsApp
Keep up with all the latest news from the UK and around the world by following Sky News
He added: "That's why the NCSC, along with our partners in Five Eyes countries, is strongly encouraging organisations and individuals to act on the guidance set out in this advisory, which includes applying updates to internet-connected devices, to help prevent their devices from joining a botnet."