Christina Mennella was just 12 when she met Tim. He was charming, handsome, and kind. Mennella, the daughter of an alcoholic father and a sometimes violent mother, was flattered by the 19-year-old’s attention. Tim’s interest made Mennella feel less alone. Little did she know that it was all a ruse. Tim didn’t want a girlfriend, he wanted a young girl whose body he could sell to strangers for profit. What Mennella interpreted as love was really just manipulation and grooming.

Tim slowly broke Mennella down, forcing her to drink until she vomited and to smoke crack cocaine. He introduced her to “friends” who taught her how to satisfy clients. At 13, Mennella stood in front of her trailer park offering her body for cash — money that Tim and others immediately took from her. Bloody beatings and threats became the norm.

For the next five years, Mennella was a prisoner, passed from one trafficker to the next, sometimes having sex with dozens of men a day. “I had to do whatever they wanted,” said Mennella, who cannot remember all that happened in that period. “They told me I wouldn’t eat if I didn’t.”

At 18, she had a son and managed to get out. She eventually earned a degree in digital journalism from George Mason University. But the nightmare didn’t really end. Now 38, Mennella suffers from post-traumatic stress disorder and experiences painful flashbacks.

“I don’t trust. I don’t talk. I don’t feel,” said Mennella, who now lives in Virginia. “I have to find a way to heal my inner child.”

Finding Hidden Patterns

Polaris, a leader in the global fight against trafficking, estimates that there are hundreds of thousands of victims of sex and labor trafficking in the United States alone. The majority are believed to be American citizens. Worldwide, the International Labor Organization reported in 2014 that forced commercial sex brought in $99 billion.

Runaways, foster kids, LGBTQ youth rejected by their parents, and those who have been sexually or emotionally abused are the most vulnerable to being recruited and exploited. Easily manipulated by traffickers who keep them psychologically off balance with a mixture of threats, flattery and false promises of love, many of these young people grow into broken adults with criminal records for prostitution and vagrancy.

“So, instead of just being child victims of trafficking, they end up being adult victims of trafficking,” said Terry Palmer, the national director of Backyard Broadcast, a Salt Lake City-based organization that fights sex trafficking through education. “They often don’t get off the streets at all.”

Added Kimberly Mehlman-Orozco, a human trafficking expert and author of “Hidden in Plain Sight: America’s Slaves of the New Millennium: “Although we supposedly abolished slavery with the 13th Amendment, that kind of abuse and exploitation still exists.”

Against this grim backdrop, a team of researchers at USC Viterbi’s Information Sciences Institute (ISI) created software called DIG that helps investigators quickly scour the internet to identify possible sex traffickers and begin the process of capturing, charging and convicting them.

Law enforcement agencies across the country, including New York City, have used DIG as well as other software programs spawned by Memex, a Defense Advanced Research Projects Agency (DARPA)-funded program aimed at developing internet search tools to help investigators thwart sex trafficking, among other illegal activities. The specialized software has triggered more than 300 investigations and helped secure 18 felony sex-trafficking convictions, according to Wade Shen, program manager in DARPA’s Information Innovation Office and Memex program leader. It has also helped free several victims.

The advent of the internet has increased sex trafficking in the United States and elsewhere by allowing traffickers to reach more people over a greater area than ever before. It also makes it easier for them to recruit youth on social media through false promises and deception. The internet’s sheer size makes it easy for traffickers to hide in plain sight. That’s because the number of online sex ads runs in the millions and grows by the minute, making it difficult for law enforcement to track traffickers and their victims.

Traffickers go to great lengths to obscure their online identities. To make their escort ads less searchable on Google, Yahoo and other popular search engines, they frequently change contact phone numbers and alter the content in their online postings. They also advertise on Backpage and other sites that are a low priority for indexing bots.

“To be a trafficker, by nature you have to be pretty intelligent and very cunning,” said Mehlman-Orozco. “Otherwise, they wouldn’t be able to control, exploit and manipulate to the extent that they do.”

DIG, which has received several upgrades since the project began in 2015, leverages machine learning to comb through millions of escort ads to mine, decode and organize information into an easily searchable database. In other words, the software helps law enforcement cut through the digital clutter to find relevant information, said Pedro Szekely, DIG’s project leader and a research associate professor of computer science.

Law enforcement agencies can tailor searches in myriad ways, including by age, ethnicity, race, geography, phone numbers, services provided, review sites, photos, email addresses and so on. They can even search for a particular person using facial recognition technology.

“If you know how to use Amazon, you could figure out how to use DIG,” Szekely said.

DIG uses a database of 130 million online sex ads and reviews that grows at a rate of 5,000 per hour. The software’s algorithms “make information extraction accurate, seamless and fast,” said ISI computer scientist Mayank Kejriwal. “There is nothing that comes close to this.”

DIG can find hidden patterns that can connect escort ads across multiple geographic locations to the same sex traffickers or victims. The software has advanced so quickly that it could soon help investigators identify “stables” of sex victims by cross-referencing phone numbers and other data to track their movements, Kejriwal explained.

“USC and ISI contributed many advances to the Memex program,” Shen said. “DIG in particular was the first user interface that enabled easy query and interaction of indexes created under Memex.”

In the absence of DIG and other Memex software, an investigator following a lead might plug a suspected sex trafficker’s name or an email associated with him into a search engine. The detective would then have to sift through the hundreds or thousands of results to hunt for more clues, a time-consuming and highly inefficient process.

Over the past three years, DIG has received about $7 million in DARPA funding, including a recent grant of $400,000.

Real Impact

The Manhattan District Attorney’s Office, among others, has been quite satisfied with DIG.

In 2015, Manhattan District Attorney Cyrus R. Vance Jr. announced that Memex, including DIG, was being used in every human trafficking case brought by the DA’s office. “With technology like Memex,” he said, “we are better able to serve trafficking victims and build strong cases against their traffickers.”

In one case in 2014, a trafficker named Froilan Rosado sat outside a Manhattan sex hotel in an idling van while an 18-year-old who worked for him, “Flora,” was inside, according to “Popular Science” magazine. Arrested by undercover cops, Flora told investigators that Rosado lured girls and women through social media. Rosado kept his victims compliant through promises of riches, drugs and threats of violence, even choking a girl who once disobeyed him. Rosado posted their photos on Backpage sex ads with contact information.

Vance wanted to find more of Rosado’s victims, but the trafficker proved quite adept at covering his digital tracks. He was equally brazen, continuing to run his business over the phone from New York City’s Rikers Island jail.

Investigators turned to an early version of DIG and TellFinder, another Memex software product, to comb through Rosado’s escort ads, turning up phone numbers, emails and photos, and more girls. Their efforts helped them identify additional victims.

In September 2015, Rosado was sentenced to 7 to 14 years in state prison for running a prostitution ring with 10 teenagers ranging in age from 15 to 18, and for trafficking an 18-year-old. New York is one of a handful of states that require proof of coercion or fraud for a sex trafficking conviction, even when the victim is a child.

“This is the most rewarding project I’ve ever worked on,” DIG’s Szekely said. “It’s really made a difference.”