Internet security experts are urging people to update their software to protect against a serious vulnerability, which if exploited could spread uncontrollably via the common wireless technology bluetooth.

The so-called 'BlueBorne vulnerability' could allow hackers to spread from device to device over bluetooth without the owner's knowledge.

Ty Miller, managing director of international cyber security firm Threat Intelligence, said this could be one of the most dangerous security flaws that has come out to date.

The vulnerability is considered serious, as the researchers who found it say an exploit could spread without people clicking on a link or being on the internet.

"It's estimated to potentially affect up to 8 billion around the world, and that's because it's got the capability to infect Window, Linux, Android and iOS devices prior to iOS 10," he said.

"So the latest iOS isn't affected."

BlueBorne was identified by researchers from Armis Labs, who alerted tech companies as far back as April, so security patches and upgrades could be created before hackers had the chance to exploit it.

But even though there are security patches available, experts warn of potentially billions of unprotected systems that could remain vulnerable to a BlueBorne attack.

So how does it work?

Armis Labs said unlike regular cyber-attacks, a BlueBorne attack can target any vulnerable device that has bluetooth.

It gets into devices from phones to printers, computers and smart TVs by exploiting a weakness in the bluetooth software.

According to Armis Labs, any attack that exploits the vulnerability — of which none is currently known — could spread over the air.

"You could be simply walking down the street [and] you walk past someone who is vulnerable and suddenly they are infected," Mr Miller said.

He said as people pass each other by, the virus passes undetected over bluetooth and without permission.

"As that keeps going on more and more people would become infected without even knowing it," Mr Miller said.

BlueBorne 'the tip of the iceberg'

The good news is security researchers detected it before hackers had a chance to exploit it, and they have alerted tech companies.

But Mr Miller said the spread of infection is still possible because people are often slack about updating their security software and operating systems.

"Or when you start looking at your printers, the new TVs, new watches, home system, the medical appliances — they don't tend to get updated because they just sit there and people forget about them," he said.

Armis Labs claims its discovery could be the tip of the iceberg.

"There could be quite a few more coming after this," Mr Miller said.