Twitter Inc. co-founder Biz Stone said that the denial-of-service attack that knocked the microblogging site offline last week convinced him that the company has to quickly muscle up to deal with its phenomenal popularity and the problems it brings.

In an interview on the PBS television show Tavis Smiley, slated to air tonight, Stone discussed last week's DDoS attack on Twitter that brought the site down for two hours, leaving many of its 45 million users adrift without a way to tweet to their followers.

It's not clear when the PBS interview was taped -- Stone talked about last week's DDoS attack but doesn't mention a second attack on Twitter yesterday. This week's attack shut down the site for about half an hour. Security analysts say it's not yet clear if the two attacks are related.

Stone said Twitter's staff of about 50 people has been working over the past year simply to deal with the site's ever-expanding popularity. And there's been a lot of growth to contend with. Last month, the Nielsen Co. reported that while Twitter is only the fifth most popular social network, its users increased their time on the site by 3,712% year-over-year.

In the interview, Stone noted that Twitter's popularity is good for business, but also increases the chance of being hit by hackers.

"So what we have learned from this, is that you have to tune your systems to handle this level of assault, this scale of assault," he said. "We spent a lot of 2008 catching up with a lot of the popularity of Twitter, the unexpected popularity -- getting there technically, so that we were stable. And along comes this massive attack. You know, we learned. We worked behind the scenes with folks from Google and other companies to figure out how to stop the attacks and how to better deal with them in the future."

In a change of topic, Stone also talked about the moment that he realized that Twitter could be a really successful enterprise.

He explained that they had just built the prototype and had asked colleagues to try it out over the weekend while he battled to rip up carpeting in a house he and his wife had just moved into.

"It was a heat wave in Berkeley at the time. It was just terrible work," he told Smiley. "I mean, I was sweating. I was discovering things underneath the carpet that I did not want to be discovering and I was cursing, 'Why did we buy this house?' And my phone buzzed in my pocket. I took it out and it was Evan [Williams], my other co-founder, and he said, 'Sipping Pinot Noir after a massage in Napa Valley.' And I laughed out loud and I just thought, 'This is so funny that he's doing that now and I'm doing this.' It made me laugh. And that laughter signaled to me that this is a product I want to work on."