c.2013 New York Times News Service

As the summer concert season approaches, live music fans, and the concert industry that serves them, have a common enemy in New York. And in Russia. And in India.

That enemy is the bot.

“Bots,” computer programs used by advanced scalpers, are a hidden part of a miserable ritual that plays out online nearly every week in which tickets to hot shows seem to vanish instantly. Long a nuisance to the live music industry, these cheap and widely available programs are now perhaps its most reviled foe, frustrating fans and feeding a multibillion-dollar secondary market for tickets.

According to Ticketmaster, bots have been used to buy more than 60 percent of the most desirable tickets for some shows; in a recent lawsuit, the company accused one group of scalpers of using bots to request up to 200,000 tickets a day.

Ticketmaster and its parent company, Live Nation Entertainment, have stepped up efforts to combat bots, in part to improve the ticket-buying experience for concertgoers, but also to burnish the company’s reputation with consumers. The result has been a game of cat and mouse between the company and the bots.

“As with hackers, you can solve it today, and they’re rewriting code tomorrow,” said Michael Rapino, Live Nation’s chief executive. “Thus the arms race.”

In late 2011, Ticketmaster hired John Carnahan, a machine learning expert who fought online advertising scams at Yahoo, to lead its anti-bot effort. By monitoring the behavior of each visitor to Ticketmaster’s site, the company can determine the likelihood of a customer being human or a machine. For example, a human may click a series of buttons at a range of speeds and in different spots on a screen, but bots can give themselves away by rapidly clicking on precisely the same spot.

A screen on Carnahan’s desk in Los Angeles shows Ticketmaster’s incoming traffic, with a rainbow of colors at the bottom and splotches of red on top representing suspicious activity. On a recent Thursday afternoon, the screen showed that the red visitors were making 600 times more ticket requests than those the system identified as being most likely human.

Bots are not kicked off the system, but rather “speedbumped” — slowed down, sent to the end of the line or given some other means of interference, to allow a regular customer through.

“We’re not trying to stop anybody from buying tickets,” Carnahan said. “We’re just trying to make sure that a fan can buy the tickets.”