This story will probably hit the papers any day now. An unspecified and dangerous loophole has been announced that will allow fraudsters to direct you to their own fake web sites even though you are using a genuine web address. In simple terms, it's as if they have found a way to get the directory enquiries operator to give you a fake telephone number. Everyone trusts the directory enquiries operator, so it's a serious breach in security.

What can you do about it? Almost nothing, just be aware of the risk until the loophole has been closed and follow the advice below. You are most at risk if you are outside America or Europe, or perhaps logging-on at an Internet cafe or using WiFi at an airport or hotel. If you attempt to log-on to any financial institution and it doesn't accept your login and password, be suspicious. It might be wise to contact them and check, they should know from the storm of irate phone calls they will receive if they have been targeted. They can reset your password and check for any fraudulent activity in that case.

This is essentially a race against time, all the major Internet service providers (ISPs) have already fixed the problem, many others are working on it, but many in the further-flung reaches of the Internet will take weeks or maybe months to "get around to it". That is because of the way the names-to-numbers information is distributed around the Internet, and the lax way that some ISPs in remote parts of world behave.

If you'd like an explanation, here it is:

When you type-in a web address, such as www.natwest.com, your computer needs to look it up somewhere to get a number that tells it where to find that specific site. In this case it ought to be: 155.136.80.213 and that's where your browser will take you. Where it looks for that number depends on how you are connecting to the Internet because the index of names-to-numbers is distributed across nine million computers located all around the world. Your computer goes to the one designated by the ISP you are using. If you are in the UK and you are using BT, for example, then it will access one of theirs and you will be safe.

If you are sitting in a dodgy-looking cyber cafe and you don't know who you are using, you cannot know if you are safe. It doesn't matter who your ISP is at home or at work: if you're not at home or work it depends on who you are using at that time. So the number that gets returned might be 123.45.67.890 - but you would not know that and your computer will take you to a site that looks like the one you want to go to. You then unwittingly type in your login and password details, and it's pay day again for another fraudster.

Do please be cautious.