Linux vendors and big web service providers are racing to mitigate the impact of the Shellshock bug, which affects millions if not billions of systems ranging from Linux desktops and servers to Apple computers running Mac OS X, and many internet-of-things devices.

This vulnerability, which affects the widely used “bash” shell, or command line interface, affects Unix-based systems. It may have been around for as long as 25 years — while it will be impossible to know about most historical exploitations, if indeed they exist, its public exposure this week means criminals will be scrambling to take advantage of it.

Unfortunately, that’s easy for them to do, and this could mean stealing information, propagating malware across systems and taking over users’ computers. Shellshock is really, really nasty, and here’s a run-down of the most important reactions we’ve seen so far:

• [company]Google[/company] has “taken steps to fix the bug in…