On Facebook, more than a million people checked in to the Standing Rock Sioux Reservation in North Dakota on Monday but that didn’t mean that many people were actually at the site.

As the Guardian reported, the action was an act of solidarity with indigenous water protectors and activists fighting the Dakota Access Pipeline, inspired by a viral Facebook post that began circulating from an unidentified source on Sunday, to thwart suspected surveillance efforts by the Morton County Sheriff’s Department:

The Morton County Sheriff's Department has been using Facebook check-ins to find out who is at Standing Rock in order to target them in attempts to disrupt the prayer camps. SO Water Protectors are calling on EVERYONE to check-in at Standing Rock, ND to overwhelm and confuse them. This is concrete action that can protect people putting their bodies and well-beings on the line that we can do without leaving our homes. Will you join me in Standing Rock? If you're sharing your location at Standing Stock: 1) Make it public. 2) Make the clarification post SEPARATE, and limit post visibility to your friends only. 3) Don't clarify on your check-in post; privately message friends who say "stay safe!" to let them know what's up. 4) Copy/paste to share clarification messages (like this one) because making it public blows our cover. 5) Use an alternate name in clarification posts so that when they filter out / search those terms, your post is visible to the right people.

The plea comes at a crucial moment. Since March, the Standing Rock Sioux, other indigenous communities, and allies have been fighting against the construction of a 1,172-mile pipeline transporting crude oil projected to run under the Missouri River that threatens the local water supply and sacred ancestral burial land.

But in recent months the tensions between water protectors and law enforcement have escalated. The contractors behind the Dakota Access Pipeline have hired security staff, which have reportedly used dogs to attack activists. Over 100 people were arrested on October 24. At least 141 people were then arrested all at once during a camp raid three days later. There have also been reports of law enforcement in riot gear, armored vehicles, and subjecting people to solitary confinement and strip searches while in police custody.

The Morton County Sheriff’s Office issued a statement on Facebook noting that the agency “is not and does not follow Facebook check-ins for the protest camp or any location. This claim/rumor is absolutely false.”

Their response, however, doesn’t make protesters any less skeptical. As burgeoning social movements use social media like Twitter, Instagram, and Facebook as a decentralized organizing strategy, it’s become clear that government surveillance of activists still occurs.

Social media has become a double-edged sword for activism

Platforms like Twitter and Facebook have become crucial ways for people to participate in and organize contemporary social justice movements.

Even though “hashtag activism” has been used to demoralize a new generation of activists, social media tools like hashtags have allowed people to organize and amplify their messages beyond their local physical community and network faster than ever. Social media has also democratized who bears witness to these events and how.

For instance, it’s hard to imagine America’s current conversation about police brutality had it not been for the social media savvy of people on the ground in places like Ferguson, Missouri, and Baltimore, and people tweeting out the names of victims like Mike Brown, Freddie Gray, Sandra Bland, and countless others to show how frequent and pervasive police violence really is.

Yet while law enforcement have used social media to target criminals, activists have also been monitored on these platforms for their organizing efforts.

In December 2014, reports emerged of the Chicago Police Department using stingray technology to eavesdrop on local protests. George Joseph reported for the Intercept last July that DHS monitored the Twitter and Vine accounts of protesters in Ferguson, Missouri. Mother Jones reported that Zero Fox, a cybersecurity firm, identified activists DeRay Mckesson and Johnetta Elzie as "threat actors" during protests in Baltimore last year. In August 2015, Vice reported that DHS was monitoring Mckesson's activities on social media.

A recent lawsuit filed against the FBI and the Department of Homeland Security by Color of Change and the Center for Constitutional Rights highlights the problem with surveilling activists in the movement for black lives: “monitoring [the movement for black lives’] legitimate protest activities with the same surveillance methods used to target and disrupt potential terrorists undermines the First Amendment’s robust protection of political speech.”

Organizers and water protectors at Standing Rock have been organizing and amplifying their message with #NoDAPL hashtag. In addition to providing updates on resources needed and information about possible police abuses, people are discussing how their current fight for clean water reflects the ways indigenous communities are fighting on the frontline against climate change in part because they have been systemically denied tribal sovereignty over their land since European settler colonialism.

But, as the Facebook post noted, indigenous activists express concerns that that law enforcement is using social media for surveillance.

“There is no doubt that law enforcement comb social media for incriminating material and monitor communications,” a unnamed representative of the Standing Rock Camp, one of at least eight resistance camps, told Snopes. “There is no solid line between ‘organizers’ and ‘others’ — this is a movement, not an organization. There are many camps and points of contact, we can only verify that it did not originate from the Sacred Stone Camp FB page. We support the tactic, and think it is a great way to express solidarity.”

Social media is, without a doubt, an invaluable organizing resource today. At the very least, the viral Facebook post provided an opportunity for people gain more awareness about Standing Rock, allowing some to provide virtual support when social media may be their closest source of contact.

But as Katie Mossett, a Native American activist, told the Guardian, one of the uncomfortable undertones of the post is the reminder that federal and local law enforcement agencies’ have consistently used surveillance strategies to thwart activist efforts.

“I think they’re listening to us right now as we speak,” Mossett said. “My concern is the invasion of privacy … It’s eerie and frankly quite irritating.”