As the email scandal surrounding ex-CIA boss David Petraeus proves, those who decide to cheat on their spouses, as careful as they may think they are, have a difficult time escaping the trail of evidence they leave behind in the online world.

Whether it's through posting intimate pictures on Facebook and Twitter, or sending out sexually explicit  texts, emails or instant messages, adulterers are creating an electronic footprint that can sometimes easily be traced back to them.

In the Petraeus case, it was email that led to the downfall of the former general. An FBI probe into harassing emails sent to a female friend of his, a Tampa woman named Jill Kelley, eventually led agents to Petraeus's biographer, Paula Broadwell. From there, they discovered the biographer was exchanging intimate messages within a private gmail account, belonging to Petraeus.

(Adding to the confusion in this case, the top U.S. commander in Afghanistan, Gen. John Allen, is now accused of sending innappropriate emails to Kelley, who used to organize social events at MacDill Air Force Base in Tampa, Fla., where both Petraeus and Allen had been based.)

"Anything you do online, with technology, there's a trail that you're leaving behind, it doesn't matter how you protect yourself," said Stan Mrovic, owner of SINTRACK, an investigation agency based in Richmond Hill, Ont., told CBC News.

"People seem to have the illusion of being private when they talk to someone or interact with someone online," Mrovic said. "It gives them the distance, the fake perception of not being there. Through face-to-face interaction, people will not say things that they will have no problem saying or admitting to online through chat groups and forums."

In addition, social media seems to be playing an increasing role in the destruction of relationships.  

si-jill-kelley

Jill Kelley is identified as the woman who allegedly received harassing emails from Gen. David Petraeus' paramour, Paula Broadwell. Kelley serves as an unpaid social liaison to MacDill Air Force Base in Tampa. (Chris O'Meara/Associated Press)

In a 2010 survey of the American Academy of Matrimonial Lawyers, 81 per cent  of divorce attorneys said they had seen an increase in the number of cases over the past five years that relied on evidence from social networking sites, with Facebook being the number one source.

Indeed, a new popular website is Facebookcheating.com, created after the founder's ex-wife had an affair with a former boyfriend she had reconnected with on the social media site.

Spy-tech

Petraeus isn't the first high-profile figure to be felled by salacious online communication. Former Democratic congressman Anthony Weiner resigned after it was discovered he had sent sexually explicit messages and photos of himself to women via Twitter and email.

Former Detroit mayor Kwame Kilpatrick got hammered after the Detroit Free Press published sexually explicit text messages between him and his former top aide, contradicting their denial of an affair.

And while not an affair, Florida congressman Mark Foley resigned after the discovery of emails and instant messages he had sent to congressional pages.

"Facebook hangs a lot of people. Twitter hangs a lot of people. Text messages are destroying a lot of families and destroying marriages," said Ken Willett, director of operations for Toronto-based Tattletales investigation agency.

Willett said that the advent of social media has actually had an impact on the investigating  business.

"We watched it from a time where you had to be out in the field and you had to be doing surveillance and watching and following and there was a lot of money spent on nothing.

"Now what's happened with the electronic world, it's taken some of the business away from us because people are now able to do a lot of it on their own.

"An example of that is simply picking up your husband's cellphone that doesn't have a password or he doesn't lock the keyboard and he jumps in the shower. We hear it everyday.

"Or the unsuspecting wife who goes out to get the garbage cans, leaves her cellphone in her purse and the husband grabs it and flips to the text messages and lo and behold the last text message is a loving message that may contain sexual content that wasn't from him."

Those who suspect infidelity can also purchase computer monitoring software to keep track of their spouse's online activities. For example, key tracer spyware plugs into the back of the keyboard and tracks every key stroke, stores it on the hard drive and will retype out every key stroke a person has made in the  past three weeks. (The founder of Facebookcheating.com said he used this technology to discover his wife's affair.)

As well, people can install ghost spyware to record and send all incoming and outgoing emails.

Willett said none of this software is illegal, provided the person who installs the software owns the computer.

At the Spytech store in Toronto, owner Ursula Lebana said although most purchase this type of software to monitor the internet activities of their children or employees, some will use it on a spouse suspected of having an affair.

Some people also use GPS trackers, which are designed to help locate vehicles if they are stolen. While illegal to put a tracker in someone else's car, you can put it on your own vehicle.

Lebana said her store, open since 1991, is as popular as ever. "New cheaters are born every day." 

With files from The Associated Press