A distributed denial of service (DDoS) attack hit a number of major retail Web sites recently during the holiday shopping rush.

"People trying to shop on Amazon, Wal-Mart and Gap, as well as users of Salesforce.com and popular travel site Expedia experienced general sluggishness and outages as a result of the flood of malicious traffic directed at UltraDNS, a registrar service that resolves the high profile website addresses," according to SearchSecurity.com.

"In a message on Twitter, Jeff Barr of Amazon Web Services said the outages were limited and affected mainly Northern California," the article states. "The attack also briefly affected Amazon's S3 and EC2 services as well."

Click here to read the SearchSecurity.com article.