The six days of online brownouts and slowdowns that have plagued Bank of America's website are "unprecedented," a leading Internet and mobile cloud monitoring service said today.

"I don't think we've seen as significant and as long an outage with any bank. And I've been with Keynote for 16 years now," said Shawn White, vice president of operations for web monitoring service Keynote Systems. "It's particularly shocking precisely because these banks know how critical it is for their online customers to be able to access their bank account. It's so personal and dear to them."

Bank of America (BofA) said its Web and mobile services have not been hit by hacking or denial-of-service attacks. But the nation's largest bank would not disclose what's causing its online problems.

The bank also said it has substituted its standard homepage with an alternate one to help in user navigation.

"I just want to be really clear. Every indication [is that] recent performance issues have not been the result of hacking, malware or denial of service," said BofA spokeswoman Tara Burke. "We've had some intermittent or sporadic slowness. We don't break out the root cause."

A screenshot of Bank of America's homepage earlier this week

According to Keynote, BofA's online banking website has been experiencing a pattern of service disruption that has repeated itself every day since last Friday. Each morning, between 8:00 a.m. and 9:30 a.m. ET, the bank's homepage becomes slow -- so slow that transaction testing algorithms have timed out after 60 seconds of not being able to access a page.

"This is a huge problem," said Dan Berkowitz, director of corporate communications with Keynote. "I can't get into my account. This has been going on for six days. This is the most unprecedented banking outage we've ever seen at Keynote. We've never seen anything this extensive, ever."

Keynote has 4,000 servers in 50 cities around the world that test thousands of websites every five to 15 minutes, collecting 550 million performance measurements daily. In the U.S., Keynote continually tests sites from 10 cities around the country.

In the case of BofA, Keynote's testing algorithm accesses the bank's homepage, goes to the online banking page and enters log-in information. It then drills down into account history and logs out. It is a five-webpage test, "very typical of what you or I would do," White said.

"Early in the morning between 8 a.m. and 9 a.m. -- this morning it was at 8:13 a.m. -- the site becomes very slow, ranging from 15 to 20 seconds all the way down to 60 seconds to complete this five-page transaction. It was to the point where our measurement agents just gave up," White said. "Imagine you or I would give up after five or 10 seconds or hit the refresh button."

White said that at 9:12 a.m. ET today, BofA updated its homepage with a "friendly" message saying it was experiencing performance slowdowns, and offering links for the most popular web pages, such as ATM locations or loan information.

"That's a pretty surprising response in that Bank of America is a very big brand and their homepage is normally very colorful, very inviting, and it has a lot of interaction. Now they've replaced it with a very fast loading, sparse message," White said. "For the largest bank in the U.S. to do this, it's like being in a big shopping mall during the holiday season and they took down all the Christmas decorations and put armed guards outside the stores. I'd find that surprising."

According to Alexa Web monitoring services, Bank of America's website woes are number six in a list of hot Internet topics, right behind Apple's new iPhone 4S and Amanda Knox, the American student just released from an Italian prison after her murder conviction was overturned by an appeals court.

Speculation ran high that hackers might be causing service disruptions after problems with BofA's website began last Friday and continued over the weekend into this week.

In published interviews earlier this week, Burke said BofA had simply taken some "proactive measures to manage customer traffic during peak hours during the day," and that had resulted in slowness.

Today, she was less forthcoming about what was causing the problems.

BofA launched a new temporary homepage to help direct customers to popular services

"We began seeing some sporadic issues on Friday. We're not going to get into the technical details. We're not going to comment on the technicalities of what we do," she said. "Given the last few days, what you're seeing today is we're rigorously monitoring the online banking space, and we chose to deploy an alternate homepage. The reason for this is to ensure customers get to their right destination quickly.

"We continue to assess the situation," she added.