A worrying new security vulnerability means that all Apple Mac computers, about half of all websites, and even internet connected home appliances are all vulnerable to hackers. Security experts are saying it's even worse than this year's Heartbleed fiasco. But what is Shellshock exactly, and what does it mean for the security of your business?

Shellshock exploits a vulnerability in Bash. Bash, an acronym for Bourne Again Shell, is a command-line shell used by many UNIX computers. UNIX is an operating system on which many others are built, such as Linux and Mac OS. So if any part of your business runs on a Unix-based operating system, it could be vulnerable.

Bash is a key component of the web servers that run at least half of the websites on the internet, so if downtime on your website is a concern, you need to get yourself protected. Even if you don't use any aspect of Linux yourself, a huge proportion of the Internet runs on the "backbone" of Apache, which uses Bash heavily. Bash is also used in the background by web browsers, email apps, FTP (website upload) apps and all kinds of other applications.

If you're not sure if your website is supported by Apache, contact your server operators and find out. Check that they are enacting a patch that will keep the criminals away from your website.

The real problem is just how easy it is to do. It only takes about three lines of code to attack a vulnerable server, which means attacks based on the vulnerability are well within the reach of even pedestrian hackers and cybercriminals.

Any sensitive files also need to be audited and secured, if you believe you could be compromised. Not only does Shellshock allow hackers to read information, it can write, copy and delete files -- and worst of all, run programs, without the user ever knowing it's happened. Anything that your business couldn't operate without -- that is, your highest priority in terms of data security -- might need to be taken off the network until the vulnerability is fixed.

If your data really can't be compromised, it's worth copying your sensitive data to a USB key or CD (with multiple copies for backup), and remove them from networked computers. Businesses should also be on heightened alert: they should look to their monitoring and web application firewalls to look out for any attacks.

For Mac users, you should look for the latest update to OS X, which hasn't arrived yet -- but should be coming soon. As for the rest of the Internet -- let's hope it gets fixed soon!

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