Did you get an email saying your order from Walmart, CostCo, or Best Buy was cancelled? If so, you might have malware installed on your computer.
Hoax Slayer is reporting a large number of people have received an email claiming their order was cancelled because of a bad address with a link to click to correct the issue. Clicking the link downloads software that could steal your passwords and send them to criminals.
If you received and email like this or believe you could be at risk, run your antivirus program immediately.