Wells Fargo's online banking site was experiencing problems Tuesday, with a denial-of-service attack likely the reason behind the slowdowns for some customers trying to access the site.
"Today we’ve seen an unusually high volume of website traffic which we believe is a denial of service attack," a bank spokesperson told NBC News. "The vast majority of customers are not impacted and customer information is safe."
Customers who are having problems logging on are encouraged to do keep trying, "as the disruption is usually intermittent," the spokesperson said. "We apologize to our customers for any inconvenience."
This isn't the first time the bank site has been under a denial-of-service attack, where hackers inundate a website with traffic to delay or disrupt it.
Bank of America, JPMorgan Chase, Ally Financial, and regional bank BB&T have also been hit with attacks in the past year. Sources have previously told NBC News and Reuters that the attacks may be part of an effort by Iranian hackers against major U.S. financial institutions and other corporate entities.
Last fall, a financial services industry group, the Financial Services Information Sharing and Analysis Center, issued an alert about the attacks to members, raising the threat level from "elevated" to high," because of "credible intelligence" about the potential for such attacks.
