Thanks to three Bowdoin students, police departments worldwide are fighting child pornography faster and with greater ease.

Last fall, senior computer science majors Nick Dunn, Tucker Hermans, and Jeremy Fishman wrote a computer program that helps recover deleted video files from child pornography suspects' hard drives. Their collaboration arose in November in response to a request from Sergeant Glenn Lang, supervisor of the Maine State Police Computer Crimes Unit. Lang had contacted both Chair of the Computer Science Department Stephen M. Majercik and a University of Maine professor in his search for a program that could help the police in child pornography cases.

"I e-mailed Sergeant Lang's request for assistance to our computer science majors and minors, and less than an hour later, I was copied on an e-mail Nick had sent Sergeant Lang saying he would be happy to help him," said Majercik.

"We had a specific need: to take manual labor out of carving bits of data out of child pornography," said Lang. The specifications he sent by e-mail required skills that Dunn, Hermans, and Fishman had in their arsenal.

"I was in the [robotics] lab with the other guys, and we thought that what they needed wouldn't be too difficult. We had the expertise and the time, so we figured we would just throw something together," said Dunn.

Similarly, Hermans said, "I thought [the e-mail] was interesting because it was very specific in what it wanted. It didn't seem that difficult to implement. The tools it wanted were pre-existent and just needed to be put together."

The Harvester, which Lang named the program, works in conjunction with software that the Maine police already had. According to Dunn, it detects files that have been erased or renamed, extracts bites from them, and makes cryptographic hashes, with which the police can make a database. Essentially, it creates digital fingerprints, different for each file, which can be matched against pre-existing files. Therefore, the police can detect if a suspect has a known child pornography file on their computer without going through every file.

"Our program doesn't do any recovery itself, but what it spits out can be input in files police already have," said Dunn.

According to Lang, his department, which does not staff any computer programmers, previously employed a labor-intensive process that took months to recover deleted files.

"I'm surprised that it hadn't been made. In some way they had been doing it by hand," Hermans said. "There are commercially available forensic computer tools, but no existing programs that packaged the program in this way. It made the process a lot faster and a lot more manageable."

The students sent Lang the first version of the program within four days of his inquiry. They then worked on and off for the next month in response to Lang's requests for various new features. Dunn estimated that in total the program took no more than 50 hours to write.

Hermans and Fishman wrote the back-end of the program (what actually happens when you click a button) which puts out a string of numbers. Dunn, the leader of the group, fused these elements together and created the front-end (what the user sees and interacts with). He said that making the Harvester aesthetically pleasing and easy to use was the most time-consuming part of the process.

The three students worked well together, having collaborated previously as members of Bowdoin's RoboCup team, which creates robots that compete in soccer against other teams.

"We understood how to have multiple people working at the same time, and more specifically we knew what each of us could do best," said Hermans, one of the captains of the RoboCup team.

Lang and his colleagues were full of praise for the Harvester, which Lang said would be especially useful for cases in which the police know a suspect has viewed child pornography, but have no way of recovering the erased videos.

"It revolutionized the way people look for these videos," said Lang. "No one has suggested anything like this. I've been running this department since 2001 and doing computer forensics for a long time, and I've never heard of another way to accomplish what this program does."

A testament to the essential need that it fills, the Harvester is reportedly being used in 21 states and 12 countries. Lang suspected that the program has spread to even more states now, and will "absolutely" spread in the future.

Dunn, Hermans, and Fishman "have done a tremendous service to children on this planet who are being exploited," Lang said. He clarified that this tool helps to combat videos involving children from two months to ten years old.

The students have not been paid for their work. Both Dunn and Hermans said they did not intend to profit from writing this program and that their only goal is to help the Maine State Police.

"Not only our unit, but others around the country are in debt to Nick and his friends for the service they did without compensation," said Lang. "It's very rare to get people that don't get much more noble than that."

"I'm a little stunned, because I had no idea that the demand for a program like this was so widespread. This is serving the common good on about as big a scale as you can get," he said. "But, I'm not surprised that it was three Bowdoin computer science students who wrote the software."

In addition to the Harvester's most direct application to child pornography cases, it could potentially be used for any cases requiring data recovery and identification, for example corporate espionage.

Despite the students' contribution to computer forensics, Hermans said that all three of their interests lie elsewhere. Hermans, originally from Temple, Texas, plans to pursue his Ph.D. in Robotics at the Georgia Institute of Technology next year. Dunn, of Berwick, Maine, has been speaking with companies about a programming job. Fishman, a Westport, Conn. native, was unavailable for comment.

"I'm just really proud that Nick, Tucker, and Jeremy were so willing to step in and take on this project and that they did such a great job," said Majercik. "They are truly remarkable students."