Nov. 1, 2010 -- He has been called a bounty hunter for the digital era, and for good reason.

After Michael Roberts' own name was smeared across the Internet by an online antagonist, crushing his successful business and threatening personal relationships, Roberts made it his mission to help other victims of online defamation rout out the anonymous Internet trolls trying to upend their lives.

The Australian native launched a Las Vegas-based company called Rexxfield, dedicated to digital forensic analysis and online reputation defense. (Nevada was chosen as the home base because its state laws are more favorable for those suing for libel damages.)

Since starting the firm in 2008, Roberts said he has helped more than 150 people unmask their online attackers. His firm boasts an 80 to 90 percent success rate for positively identifying anonymous Internet posters. He recently launched the non-profit FreespeechV3.org, a pro bono arm of his company, to give victims of online defamation even more support.

By the time people contact him, they've been branded whores, child abusers, liars and other vicious epithets on the Internet. They're spirits are so deflated, some consider ending their lives, he said.

"You can hear it in the voice of the people when they first contact you," he said. "And once the problem is solved they're like a different person."

Billionaires, Royalty Among Those Looking to Expose Anonymous Online Harassers

Roberts counts billionaires and royalty among his clientele and two of the most recent high-profile cases involving unmasking anonymous posters were ones in which he was involved.

A couple of weeks ago, one of his pro bono clients, Carla Franklin, succeeded in obtaining a court order from a New York judge instructing Google to identify people who posted defamatory content about her on YouTube.

Another pro bono client, Vogue cover model Liskula Cohen, made headlines last summer when she successfully sued Google to uncover the name of an anonymous blogger who slandered her online.

But how does this modern-day bounty hunter track down his prey?

Roberts said it often starts with the Internet Protocol (IP) address, which is the unique number assigned to any device connected to the Internet.

IP Address Is 'Smoking Gun,' Online Investigator Says

"That's the smoking gun that inexorably links the offensive posting to the address – not the person, of course, but the address," he said.

When someone goes online and posts a comment on a website or writes a blog post, an IP address connects the computer he or she is using to a physical address. That IP address is logged both by the Internet Service Provider and by the website hosting the content.

It's the key piece of information that can pierce the so-called veil of anonymity online, but Roberts said that there's one problem: It's perishable information.

"The moment somebody posts their smear or their diatribe, the clock starts ticking," he said.

In most states, the statute of limitations for Internet libel for civil relief is one year, he said, although a few states extend the limit to two or three years.

And, he added, ISPs, search engines and other websites regularly purge their systems of IP address logs.

But IP Address Is Often Not Enough

They aren't required by law to store the information for any specific amount of time, so they set their own policies governing the deletion of files.

Roberts said that from his experience, ISPs tend to delete IP information after about six months; Web companies, such as Google, tend to hold on to information for longer.

The information held by the ISP, however, is actually more critical, he said. While an IP address stored by a website might be able to lead a forensic expert to the ISP that enabled the Internet connection, the IP address held by an ISP can actually lead the expert to an Internet troll's front door.

But Internet companies don't just hand over these keys. A subpoena and, in some cases, a court order, are necessary to force the companies to release the IP addresses.

Even after Roberts obtains the requested IP addresses, his job is not always finished.

"So many cases fail, whether it be harassment, wire fraud, whatever it might be, because it's like a doorway we know the person walked through, but so did 100 other people," he said.

An IP address can tell him where the poster's computer may be located, but it doesn't absolutely link a specific person to that computer.

To identify the individuals behind online attacks, Roberts said he uses a combination of high-tech expertise and old-fashioned instinct.

Digital Forensics, Linguistics Help Identify Online Attackers

"We have to triangulate the individual with digital evidence that can't be obtained electronically," he said.

Assuming a victim has a sense of who might be behind the attacks (which they often do, he said), he and his specialized team reach into their black box of tricks to map out the individual's social network.

Using what he called "social forensics," they figure out the person's friends, most frequented sites and habits online.

"They leave lots of electronic footprints," he said.

In 75 to 85 percent of the cases, those tactics are enough to positively identify the perpetrators of online attacks, Roberts said. But in some cases, he goes a step further, enlisting a Ph.D.-trained forensic linguist.

"[She] can examine known samples of writing with the anonymous writings and link them together with the little idiosyncrasies in the person's prose," he said.

While Roberts does take on several cases on a pro bono basis, he said, most cases cost about $5,000 to $10,000 (not including legal fees which, depending on the circumstances, can significantly inflate the price).

But his clients say that the expense is worth it.

Patty McPeak, founder of natural products company Nanacea, said that after she left her previous company, where she had been CEO, online commenters wrote vicious posts about her and her family.

The ordeal continued for about two years, but Roberts' company helped expose the commenters. And when McPeak let them know that she had learned their identities, the online onslaught stopped.

At 69-years-old, she said, she had no desire to spend her golden years suing them, but just knowing who was behind the attacks was enough.

"I would have gone to my grave wondering who would have said such awful things about me," said McPeak, who lives in El Dorado Hills, Calif. "I have such peace of mind knowing who these people are. It would never have been possible without this."