Com-Central.net

A "deadly serious" bug potentially affecting hundreds of millions of computers, servers and devices has been discovered.

The flaw has been found in a software component known as Bash, which is a part of many Linux systems as well as Apple's Mac operating system.

The bug, dubbed Shellshock, can be used to remotely take control of almost any system using Bash, researchers said.

Some experts said it was more serious than Heartbleed, discovered in April.

"Whereas something like Heartbleed was all about sniffing what was going on, this was about giving you direct access to the system," Prof Alan Woodward, a security researcher from the University of Surrey, told the BBC.

"The door's wide open."

Some 500,000 machines worldwide were thought to have been vulnerable to Heartbleed. But early estimates, which experts said were conservative, suggest that Shellshock could hit at least 500 million machines.

The problem is particularly serious given that many web servers are run using the Apache system, software which includes the Bash component.

Patch immediately

Bash - which stands for Bourne-Again SHell - is a command prompt on many Unix computers. Unix is an operating system on which many others are built, such as Linux and Mac OS.

The US Computer Emergency Readiness Team (US-Cert) issued a warning about the bug, urging system administrators to apply patches.

However, other security researchers warned that the patches were "incomplete" and would not fully secure systems.

Of particular concern to security experts is the simplicity of carrying out attacks that make use of the bug.