Sex trafficking in a US city was significantly disrupted by a non-profit group that deployed decoy chatbots in conversations with tens of thousands of men.

During a two-year period, Seattle Against Slavery posted fake online adverts that connected people with chatbots that initially posed as sex workers, before delivering a deterrence message. The campaign, which also involved placing more than 2m Google adverts warning people of the risks of buying sex online, led to a 50% decline in online searches for keywords such as “teen escort”.

Robert Beiser, former executive director at Seattle Against Slavery, who is presenting the findings at the American Association for the Advancement of Science conference in Seattle on Friday, said: “In a fairly short length of time we were able to reach hundreds of thousands of people who had searched for common terms. In Seattle, we were able to impact the marketplace pretty dramatically.”

Beiser said that, while not everyone selling sex online was a trafficking victim, internet searches were targeted because survivors of trafficking had reported that transactions were typically initiated online.

“We found it really wasn’t a hidden dark web environment that people were using to buy trafficked sex. It was as simple as Googling it,” he said. “In some cases, it would possibly be easier to order a sex-trafficking victim online than to order a pizza.”

Seattle Against Slavery won a Google ad grant, which allowed it to place free targeted adverts that would appear as sponsored links in response to common search terms such as “escort sex tonight”.

Between 2014 and 2016, 2.1m ads were placed that had simple deterrence messages such as “You could be arrested for buying sex online” or “By buying sex online you could be causing harm to a victim” and links to counselling services and other support groups. During this period there was a 40-60% decline in keyword searches – a statistically significant decline when Seattle was compared with other US cities where the digital campaign had not taken place.

“That cut off a certain fraction of the population, but then there were the people who were still going to the websites,” said Beiser.

Between 2016 and 2018 the organisation also began to post fake ads apparently offering sex that would appear in response to keyword searches. These would contain a mobile number to text, which would trigger a chatbot designed to pose as a sex worker. Beiser said that developing the chatbot was quite straightforward because the conversations were so repetitive. “There were lots of ‘Hello, where are you? What do you do? Where can I meet you?’,” he said. “The chatbot would sometimes add a little bit more colour to the conversation.”

The bots had about 19,000 conversations with 15,000 people. To test the impact of deterrence messages, in some cases, the bot would just disappear after a short chat and in other cases it would post a message stating the risks of buying sex online. Those who received such a message were 30% less likely to click on one of the ads in the future.

The decision to place decoys was not ethically fraught, Beiser said, because the ads would be visible only to people who had explicitly sought out sex online. “It was in line with an understanding that these websites have literally hundreds of thousands of ads,” he said.” “We weren’t creating a marketplace or enticing people into a behaviour.”

In the latest phase of its campaign, Seattle Against Slavery has developed a platform to help anti-trafficking support groups to reach potential trafficking victims. Using automated search methods they collected 21,000 phone numbers that appeared online on escort sites, which were used to reach out to possible victims. This prompted 2,000 responses. “There are some real opportunities to connect trafficking victims with services,” said Beiser.