Editor's note: This post was continuously updated as this story developed. For a more complete account of what happened, see our followup story here.
Update: A customer support representative for NeuStar, the company that provides the UltraDNS service, confirms the outage was the result of a DDoS (distributed denial of service) attack. More details below.
Procrastinators, beware: Amazon.com and a host of Internet shopping sites are having trouble Wednesday evening.
Two days before Christmas is likely not the best time for Amazon to go down, but at some point around 5 p.m. PST Wednesday evening, Amazon was loading extremely slowly. One CNET reader wrote in to say his pending transaction failed just as he attempted to complete it, and the site was extremely sluggish as the sun set on the West Coast Wednesday.
Twitter users of Amazon's S3 service for Web hosting reported outages as well, and customers of Salesforce.com and Walmart.com were also reporting problems on Twitter.
We'll update as we learn more. If you can't (or can) access Amazon from your location, please let us know in the comments.
Updated 5:35 p.m. PST: It appears the problem may be larger than Amazon. Reports began to immediately circulate that UltraDNS, the DNS provider for several West Coast Internet companies, was having serious problems. In addition to Amazon, Salesforce.com, and Walmart.com, problems were also reported with Expedia.com.
Rusty Hodge, general manager and program director at Internet radio station SomaFM, tweeted that UltraDNS simply went down, taking down customers of Amazon's S3 and EC2 services as well as Amazon.com itself. Jeff Barr, lead Web services evangelist at Amazon.com, retweeted Hodge's statement without comment.
In perhaps a related problem, the Internet Health Report shows severe latency and packet loss on a connection between Qwest and Savvis.
Updated 5:45 p.m. PST: UltraDNS representatives could not be reached for comment. Amazon.com, Walmart.com, and Salesforce.com all seemed to come back to life around 5:40 p.m. PST, but some problems were still being reported.
Amazon representatives did not immediately return a call seeking comment.
Updated 5:53 p.m. PST: Amazon's AWS Service Health Dashboard reports "DNS resolution errors" affecting Amazon Simple Storage Service customers for Northern California and U.S. Standard.
Updated 6:10 p.m. PST: A customer support representative for Neustar, the company that provides the UltraDNS service to several e-commerce sites, confirmed that its network was hit by a DDOS attack targeting their California network in Palo Alto and San Jose.
As of 6:15 p.m. PST, things seemed back to normal. The Internet Health Report also showed an improvement on the Qwest-Savvis line noted earlier, and Amazon's Web Services dashboard confirmed that while there were problems resolving DNS requests, "the service is successfully responding to requests."