Screenshot by Steven Musil/CNET

The Web sites for banking giant JP Morgan Chase are offline this afternoon as the result of a distributed-denial-of-service attack, a representative told CNET.

The site's usual banking tools and content were replaced this afternoon with a message that said:

Our website is temporarily down, but our branches and Mobile Apps are available. Please try again later.

The representative couldn't say how long the site had been down or how long it would be until service was resumed.

Hackers have ratcheted up their assaults on financial institutions in recent months, using DDoS attacks to take down Wells Fargo, Bank of America, Chase, Citigroup, HSBC, and others. Though initially it was unclear who was behind the attacks, government officials and security researchers said in January that Iran was responsible for these cyberattacks.

Even the U.S. Federal Reserve was not immune to hackers, suffering a security breach last month of one of its internal Web sites. That attack came on the heels of the hacking group Anonymous claiming to have published log-in and private information from more than 4,000 U.S. bank executive accounts, though it was unclear if the two events were connected.

In its December report, security company McAfee said that attacks on U.S. financial institutions are only going to increase in 2013. The firm said that this isn't just a possibility; it's a "credible threat." Anonymous has also promised to increase its activity in 2013. In a statement issued at the beginning of the year, the group said that it has no plans to fade away in the year to come.