Critics have targeted a recent study on how emotions spread on the popular social network site Facebook, complaining that some 600,000 Facebook users did not know that they were taking part in an experiment. Somewhat more disturbing, the researchers deliberately manipulated users’ feelings to measure an effect called emotional contagion.

Though Cornell University, home to at least one of the researchers, said the study received no external funding, but it turns out that the university is currently receiving Defense Department money for some extremely similar-sounding research -- the analysis of social network posts for “sentiment,” i.e. how people are feeling, in the hopes of identifying social “tipping points.”

The tipping points in question include “the 2011 Egyptian revolution, the 2011 Russian Duma elections, the 2012 Nigerian fuel subsidy crisis and the 2013 Gazi park protests in Turkey,” according to the website of the Minerva Initiative, a Defense Department social science project.

It’s the sort of work that the U.S. military has been funding for years, most famously via the open-source indicators program, an Intelligence Advanced Research Projects Activity (IARPA) program that looked at Twitter to predict social unrest.

If the idea of the government monitoring and even manipulating you on Facebook gives you a cold, creeping feeling, the bad news is that you can expect the intelligence community to spend a great deal more time and money researching sentiment and relationships via social networks like Facebook. In fact, defense contractors and high-level U.S. intelligence officials say that social network data has become one of the most important tools they use in the collecting intelligence.

Defense One recently caught up with Lt. Gen. Michael Flynn, the director of the Defense Intelligence Agency who said the U.S. military has “completely revamped” the way it collects intelligence around the existence of large, openly available data sources and especially social media like Facebook. “The information that we’re able to extract form social media -- it’s giving us insights that frankly we never had before,” he said.

In other words, the head of one of the biggest U.S. military intelligence agencies needs you on Facebook.

“Just over a decade ago, when I was a senior intelligence officer, I spent most of my time in the world of ‘ints’ -- signals intelligence imagery, human intelligence -- and used just a little bit of open-source information to enrich the assessments that we made. Fast forward to 2014 and the explosion of the information environment in just the last few years alone. Open-source now is a place I spend most of my time. The open world of information provides us most of what we need and the ‘ints’ of old, they enrich the assessments that we’re able to make from open-source information.”

Open-source intelligence can take a variety of forms, but among the most voluminous, personal and useful is Facebook and Twitter data. The availability of that sort of information is changing the way that DIA trains intelligence operatives. Long gone are the spooks of old who would fish through trash for clues on targets. Here to stay are the eyes looking through your vacation pictures.

“We train them differently even than we did a year ago because of the types of tools we have. There are adjustments to the trade craft, and that’s due to the amount of information we can now get our hands on,” Flynn said.

The growth of social media has not just changed day-to-day life at agencies like DIA, it’s also given rise to a mini gold rush in defense contracting. The military will be spending an increasing amount of the $50 billion intelligence budget on private contractors to perform open-source intelligence gathering and analysis, according to Flynn. That’s evidenced by the rise in companies eager to provide those services.

Some of them are well known like Palantir, the Silicon Valley data visualization giant that’s been featured prominently in Bloomberg Businessweek and has graced the cover of Forbes. Collecting or analyzing social network data wasn’t something they originally wanted to get into according to Bryant Chung, a Palantir employee. Palantir doesn’t market itself as a data collection company. They provide a tool set to help agencies visualize and share data.

The company worried that partnering with the intelligence community to do social network data collection could hurt their reputation among the tech community, increasingly wary of the government, according to Chung. When the company was approached by NATO and some U.S. intelligence groups, they decided to explore the marketplace for sentiment analysis of social network data.

“There are a lot of other commercial companies already in that space. Unless we know we’re going to crush it, we don’t want to get in,” Chung said. “I think we have a differentiated capability, especially at a macro level. For example, you are interested in monitoring an election somewhere in Africa and you want to know who are the people tweeting on one side of an election versus the other, or who are the most influential tweeters or you what if you have intelligence that an explosion is about to happen at a particular square, can you confirm that using Tweets?” That’s the sort of thing Palantir wants to help you with.

Many of the groups doing this sort of work on behalf of the government are small outfits you probably have never heard of. And ideally, you never would.

One of them is a company out of Austin, Texas, called SnapTrends, founded in 2012. They provide a “social listening” service that analyzes posts to provide insights about the circumstances of the poster, one of the most important of which is the poster’s location. The company uses cell tower density, social network knowhow, and various other elements to figure out who is posting what and where. Are you someone who refuses to geo-tag your tweets out of concerns for privacy? Do you turn off your phone’s GPS receiving capability to stay under the proverbial radar? It doesn’t matter to SnapTrends.

One tweet and they can find you.

“If it’s a dense environment. I can put you within a block. If it’s a [bad] environment I can put you within two or three blocks,” said Todd Robinson, director of operations for Defense Military Intelligence for the company General Dynamics Information Technology, GDIT, and SnapTrends president for Middle Eastern operations. GDIT partnered with SnapTrends to sell their services to the government. “Once I do have you, I click this button right here, I can go back five years [of social media posts.]”

SnapTrends says that the tool was extremely helpful in the investigation following the 2013 Boston Marathon bomb attacks. Using social network analysis, “we found the college kids that had access to the computers [owned by the suspects]. We were able to get to them first,” said Robins.

The use of social network data for intelligence isn’t just fair, Robbins says, it’s a no-brainer. Scrawling Facebook for clues about human behavior doesn’t require breaking in via backdoors or other elaborate pieces of technological trickery. “When you join Twitter and Facebook, you sign an agreement saying you will post that to a public web page. We just pull data from that web page.”

”I’m a retired intelligence guy,” he said. “This is not that difficult, people.”

But while social data may be an important tool in intelligence collection, it’s hardly a permanent one.

In the same way that observing the behavior of some subatomic particles changes the behavior of those particles (called the observer effect), watching the tweets and posts of targets can create an environment where people tweet less. You poison your own well by drawing from it. That happens on an individual level in terms of specific human targets but also on a larger, societal level.

“We’ve seen that already,” Robinson said. “There is always a risk that as people understand this, they’ll quit putting [posts] on there.”

The view was seconded by SnapTrends co-founder and CEO, Eric Klasson. “The more the ‘bad guys’ know about what is possible, the less they will use social media. This undermines state, local, federal and international law enforcement efforts,” he told Defense One.

When asked if he was concerned that people might stop using Facebook, Twitter and other social networks as a result of U.S. intelligence activities, Flynn answered matter-of-factly: “Yes.”

“We have to be agile enough to watch how those adaptations occur and we have to try to stay ahead of them for when we see them and adjust our capabilities to be able to understand them. People will constantly adapt to their environment in order to survive,” he said.

DIA has some time before the social network pool is spoiled. Today, Facebook remains the number one social network in the Middle East. More than 90 percent of all the Internet users of Qatar, Saudi Arabia, Lebanon, Egypt, Tunisia and the United Arab Emirates use the service.

Should millions of people decide to abandon the network and seek out another one to connect to and communicate with the outside world, the U.S. intelligence community will likely already be there.