Tomorrow is "Cyber Monday", predicted to be the busiest day ever for online shopping as people splash the cash in the run-up to Christmas.

A year ago, Amazon alone clocked 3.5 million sales on the same day in December. We will spend £10 billion shopping online this month, according to the Payments Council, a 500% increase on the tentative £300,000 spent a decade ago.

But as well as being a bonanza for retailers, our love affair with cyber-shopping brings juicy opportunities for fraudsters. Equifax, the credit check and identity fraud specialist, is urging consumers to protect their personal information in cyberspace as retailers prepare for the online shopping frenzy.

Neil Munroe at Equifax says: "While shopping online is obviously less stressful than fighting the crowds in the high street, it can bring its own stresses if shoppers aren't careful about where they share their personal financial information.

"Fraudsters trawl cyberspace for the identities of real people, enabling them to access existing bank and credit card accounts as well as set up new accounts in victims' names.

"It has been estimated that it only takes three pieces of information to steal someone's identity. And over the Christmas shopping period, they will have more opportunity than ever to take advantage, with many victims not realising they've been targeted until their credit card bills arrive next January."

Equifax offers a WebDetect alert service which can identify stolen identity credentials on networks, in chatrooms and across websites worldwide.

But consumers can take basic precautions to protect themselves without such cost. These boil down to: use sites that are familiar; have been recommended; or have authentic reviews about them.

Directory site Shopsafe.co.uk says most online problems relate to smaller, lesser-known websites. Shopsafe and Safebuy publish details of reputable sites. A Google search can also reveal whether a site is the focus of complaints on consumer forums - though even good sites can be "trolled".

On the site itself, look for a locked padlock symbol in the browser address frame. This confirms any information typed in will be transmitted securely. If the address starts with "https", the "s" also means it is secure.

If the prices on offer look too good to be true, or anything else about the site doesn't seem quite right, don't buy. You could end up with counterfeit goods - or nothing at all.

Before placing an order, read the terms and conditions, delivery information and returns policy, and make a note of the contact details in case of problems. Reputable retailers should provide a head office address, not just a PO box number, email or mobile phone number.

Take care too about how you pay. The UK Cards Association calculates that spending using stolen card numbers - known as "card not present" fraud - cost UK consumers more than £220 million last year.

Consider creating a PayPal account, which enables you to shop without divulging your financial details to the retailer. Alternatively, password protect your payment information through Verified by Visa or MasterCard SecureCode .

If you are spending more than £100, use a credit card not a debit card. Under the Consumer Credit Act, if something goes wrong with a credit card purchase over this amount, the provider is jointly liable and you can pursue it for a refund.

When you are finished shopping, always log out of the site, and save the confirmation email as proof of what you have bought and paid for.