You're watching ABC News Breakfast. Microsoft users are being warned they might need to switch from the world's most popular web browser Internet Explorer to another system. Experts are warning there's a serious security flaw that may allow hackers to access personal information. So to explain just what this means for you and your PC, we're joined in the studio now by IT expert Jeremy Howard.

Jeremy, good morning. Good morning. Now, this isn't entirely a new allegation or fear, is it? What sparked it today? Well, look, to be honest, for years security experts have been warning everybody to stop using Internet Explorer and start using something else. Firefox being the one usually suggested. This is because Internet Explorer has years of critical problems, which is putting people's data at risk.

Their internet banking passwords, for instance. The big problem today is that there is a very widely used exploit that you can't avoid if you use Internet Explorer. It's hitting people hard. Already many, many people, hundreds of thousands of people on the internet have been affected. So how serious a threat is this?

If you're logging onto your computer this morning at home to check your bank account, there's no way you should be using Internet Explorer? That's right. And normally I like to come on and talk about solutions and things people can do. But today I can't. It's very difficult because for me to say go and get Firefox, the first thing you might say is, oh, I haven't got it.

I'll go and download it. There's a problem already. Because you've used your Explorer to download it. OK, I'll just update Windows. Well, A, there is no update currently which fixes this problem. Microsoft have known about it for a few weeks and still haven't fixed it. And furthermore, even to download the fix, you would have to use Internet Explorer.

What does it actually do? What's the problem? Well, the problem is it's a generic problem called an exploit, which means that anybody can get into your computer and do whatever they want. Now, currently, most of the exploits of this particular problem, it's not a big deal. They're stealing computer game passwords.

But the problem is once that person's code is in your computer, they can go back later or they can often what happens is they'll sell what's called a botnet of infected computers to the criminal underground for lots of money. And then they go in and steal all of the banking passwords or use it to attack other computers or so forth.

So are you aware of any incidences in Australia using this system where people's personal information has been stolen? We can't know yet exactly what the hackers have done with the information. I do know that there are plenty of people in Australia that visit some of the tens of thousands of infected websites.

It's as simple as going to a website which somebody else has already hacked into that can cause this problem. So we don't know what's being done with these exploits yet. But the problem is once you've been infected, even a patch can't fix it. You have to scrub your whole computer and start again.

There's no known way to fix an infected computer. Now, not wanting to promote one brand over the other this morning here on the ABC, there's been a long been a discussion about whether Macs are now going to overtake the PC in terms of popularity and also security because they're less prone to viruses.

Is this one more death blow for Microsoft for those operating systems? Look, in this case, it's about the web browser Internet Explorer. If you don't use that and there are others like Firefox and Opera and Google's got a new one called Chrome, which are all they're more secure, they're faster and they've got more features.

So for years, Internet experts have been saying use one of these browsers instead. Eight out of 10 people still use Internet Explorer. Zero out of 10 security researchers use Internet Explorer. Using a Mac is another good way to avoid this problem. But of course, you might have all kinds of reasons like sharing office documents at work, which might need you to use a PC.

Jeremy, thanks for the advice that you could give us this morning. Thank you. Serious warning this morning.