If a company that's unfamiliar to you sends you a promotional offer, don't order any products from that company unless you do your research to make sure it actually exists.
Gift cards from online auction sites are likely to be counterfeit, so don't buy gift cards from those sites.
Spammers frequently send fake links to PayPal or eBay during the holidays. Don't follow links directly; type the url into your browser instead.
If you plan on buying from an online auction site, use a seller who has a good reputation and if you're not using a payment broker -- such as PayPal -- use your credit card. If you pay an auction seller with your debit card, you could be handing over your entire bank account. Credit card purchases can be canceled quickly if something goes wrong.
Here are some other tips from Symantec Authentication:
You'll know a website is safe from viruses or malware if it displays a trust seal or checkmark.
Before you put your credit card numbers in at a website, check the url carefully to ensure it reads "https." The "s" means all your personal information will be encrypted and kept safe from hackers.
If you still aren't sure about a website's security status, click on the padlock at the right side of your browser's address bar to see more detailed security information.