Faster than a speeding bullet, word is spreading across the Internet, through cyclist hangouts and into bike shops that all it takes to open a circular-key lock, like the one on the famous U-shaped Kryptonite-brand lock, is a ballpoint pen.

The U-shaped Kryptonite - consisting of a steel curve with a locking horizontal bar - is a must-have among serious bicyclists. It can cost more than $50, and for an extra $10 to $20, it comes with a guarantee that says the company will pay customers more than $1,000 if product failure results in the theft of a bicycle.

In recent days, bicycle chat rooms on the Internet have been flooded with irate comments from cyclists, some of whom have posted short movies of themselves picking their own locks with the hollow shaft of a Bic pen.

A spokeswoman for the Canton-based company, the country's largest bicycle-lock manufacturer, said it plans to accelerate the introduction of new versions of the lock because of the complaints.

Boston bicycle messenger John Anderson, 23, said a friend showed him how easy it was to defeat a U-lock.

"He did it in about two seconds. I was like, `You've got to be kidding me,"' he said. "People spend a couple of grand (on their bikes), so it's kind of a bummer that people can steal them so easily."

Benjamin Running, a 28-year-old graphic designer in New York, helped start the furor after he posted on the Internet a video of himself picking his own lock.

"These locks literally are viewed as the industry standard, the lock that you must have. They're recommended by every bike shop," he said. "I'm absolutely shattered by this."

Kryptonite spokeswoman Donna Tocci said in a statement that the design still provides "an effective deterrent to theft," but that the company is developing new products using a pen-proof, disc-style cylinder.

"We are accelerating the delivery of the new disc cylinder locks and we will communicate directly with our distributors, dealers and consumers within the coming days. The world just got tougher and so did our locks," the statement said.

The company made no mention of any refunds or free replacements and did not say whether it had received any reports of bikes being stolen with a ballpoint.

Kryptonite was founded in 1972 and is known as the originator of the U-shaped bicycle lock. In had sales of about $27 million in the year before it was acquired in 2001 by Ingersoll-Rand, maker of other security products such as Schlage door locks.

Neal Todrys, president of Kryptonite competitor Todson Inc., based in Foxboro, which makes the OnGuard brand of bike locks, said none of the company's current products uses circular key locks. Instead, they use flat-key locks.

He shuddered to think of the mischief possible in Boston, with its huge population of students with two-wheeled transportation.

"It came to me as a shock, because you might have thought that this would be discovered a couple of years ago. We were kind of speechless," Todrys said. "It's a scary thing. I don't wish that on anybody, or on any company for that matter."

Jon Currier, an employee at Belmont Wheelworks, said the bike store took down all the Kryptonite models with pickable locks immediately after he learned of the problem.

He said he doubts the problem will have any long-term effect on Kryptonite, because the company has fixed design flaws before that bike thieves have exploited.

"The name is the Jell-O of bike locks," he said. "They're the original and the survivors."

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Watch a video of the lock being opened by a Bic pen.