According to security consultants, kidnappers generally prey on victims more vulnerable than business travelers, who tend to limit time in dicey destinations and keep irregular schedules. But sometimes even the business class gets swept up in this rising international crime wave.

Many companies offer help in response, among them international insurance companies, secretive consultants who manage hostage situations and local outfits offering abduction prevention courses. As the Web site of Chartis, a leading underwriter of kidnapping insurance, says: “Kidnapping is not a rare occurrence; it’s big business.”

And it’s getting bigger.

Kidnapping for ransom is on the rise in many countries. In 2011, the Mexican government reported a more than 300 percent increase in the crime since 2005. The United States State Department Web site, which tracks worldwide crime trends, warns of “alarming increases” in kidnapping in Venezuela, and that abductions in Pakistan “continued to increase dramatically nationwide.” But statistics can be difficult to gather, and the numbers of victims are likely underestimated. Many released hostages refuse to report the crime; some fear attracting copycat criminals, while others distrust corrupt police who moonlight as kidnappers. In Venezuela, for instance, the State Department estimates that roughly four out of five kidnappings are not reported.

Insurance companies say business is brisk. “Kidnapping and ransom is a very profitable insurance business,” said Ana Paula Menezes, a former underwriter. Kidnap insurance policies typically include the services of response teams that coach victims’ families on everything from proof-of-life questions to ransom prices, which the policies reimburse. “Generally, the family will have someone in front of them within 24 hours,” said Jeff Green, the director of Griffin Underwriting, which specializes in kidnap and ransom insurance. He explained the kidnapping bargaining process: “It’s a business negotiation, where somebody is trying to sell something — and you know you are going to buy it, you have to buy it. But the advantage you have is that you are the only buyer, because they have no value to anyone else.”

Some response consultants deal directly with clients lacking kidnapping coverage. “It’ll cost you at least $3,000 a day, and it’s going to be money up front,” said Christopher T. Voss, an adjunct professor at Georgetown University’s McDonough School of Business and former lead international kidnapping negotiator at the Federal Bureau of Investigation.

Several security companies market antikidnapping training. For $650, Risks Incorporated in Miami, for instance, promises to teach students about the “real world of terrorism and kidnap and ransom!” And, yes, there’s an anti-kidnap app. BrickHouse Security, a surveillance emporium, sells Executrac software ($29.95 and a $19.95 monthly subscription), “a powerful, invisible application that turns any BlackBerry or smartphone into a covert GPS tracker with an emergency panic button.”

Mr. Voss questions the value of tracking technology. Kidnappers are “more and more aware these days that the phone can be tracked,” he said. He gave some advice to travelers visiting high-risk countries: “Get off the X, No. 1. The X is the spot where the kidnappers try and take you.” Mr. Voss argues that running away from abductors, if possible, can make sense.

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“Kidnappers generally don’t pursue,” said Mr. Voss. “They’re not runners. And they are not going to shoot at you. It’s a waste of ammunition and they will probably miss anyway.”

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He said he came to that controversial conclusion when a former Navy Seal trainer, a classmate of his at Harvard’s Kennedy School of Government, told him: “Let’s be honest, the Navy Seals, when we do renditions” — the spiriting of people from one nation to another — “effectively we’re doing kidnappings. Nobody is better at it than we are. We are the most organized, and not one person, not one of us, was assigned to chase anybody. If we’re not chasers, then the bad guys aren’t chasers.’”

Mr. Voss also urges business travelers to vary their routine, even if it means being intentionally late to appointments. “A good businessman is on time and consistent,” said Mr. Voss. “And a lot of businessmen are horrified at the idea of breaking out of consistency. If you vary your schedule by 10 minutes, 15 minutes, one way or the other, you can throw the bad guys off enough that they just might look for someone who is a little more precise.”

In a coming book, “International Security: Personal Protection in an Uncertain World,” Orlando Wilson, a security consultant, suggests another common-sense strategy for travelers: “Do not draw attention to yourself. Consider what you wear and drive, don’t be loud and rowdy. And don’t tell strangers too much about yourself.”

That can be a challenge in an era of oversharing. Marivel Andreu of the Celedinas Insurance Group in Miami warns against revealing to Facebook friends travel plans — or lunch plans.

Her clients, often wealthy families in Latin America, “are sharing all sorts of information, where they’re traveling, where they are, where they’re not, and, unfortunately, the kidnappers are using that information against them.”

A report, “Expatriate Risk Management: Kidnapping and Ransom,” by Richard A. Posthuma, professor of management at the University of Texas at El Paso, found that the length of time that Mexican kidnappers conducted surveillance decreased as they deploy “more sophisticated surveillance techniques,” like monitoring social media.

Julie Mulligan of Drayton Valley, Alberta, concedes she maintained a high profile while leading a Rotary Club exchange trip to Kaduna, Nigeria, in 2009. She appeared on a local TV show, and soon after kidnappers dragged her out of her host’s car. Held nearly two weeks, hobbling around on the high heels she wore when snatched, Ms. Mulligan “had some really dark moments.”

At one point, she contemplated an escape and hid keys to the house where she was held. Her guard discovered the keys and flew into a rage. “He raised his arm to hit me, and he called me ‘woman.’ ” Before that, said Ms. Mulligan, “he had been calling me ‘Auntie,’ a sign of respect for an older woman.”

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Despite the psychological scars from captivity — “Anybody that’s been kidnapped for more than 24 hours, the life that they knew is gone. It’s over,” said Mr. Voss — Ms. Mulligan says her experience actually enriched her life.

“I started writing this list of people who were part of the fabric of my life,” she said. For days, Ms. Mulligan edited the list on a piece of cardboard, stopping at 472 names. “When I got home I found out, realized, that it could have been so much bigger.” While she struggled to survive, eating little but white rice, stung by countless mosquitoes and threatened by guards the age of her children, she was “humbled” to learn that the churches in her town had united for an interdenominational prayer service. “The biggest thing that I have to say that I’ve understood is the goodness, the innate goodness of people,” she said.

Mr. de Ronde, the Dutch kidnapping victim, agrees that even brutal kidnappings can prove strangely liberating. “You feel the things that you are not doing right in your life,” he said. Before his trip to South Africa, he and his wife planned to buy a large house in Rotterdam, but after the kidnapping he canceled the contract. “We went on a holiday straight away, and we said, what do we really want to do in life? One of the things was, we can continue working, working, working. As I am married to a Chinese wife, I said I want to experience more of your culture.”

Mr. de Ronde and his family moved to China. He did not say where.