They tweet and blog about street gunfights and murders in Mexican regions plagued by the drug war, keeping people informed about gangland crimes which local newspapers are too afraid to report on.
With traditional media often intimidated by drug cartels, social media has given Mexicans a way to stay appraised about the dangers lurking in their towns and cities.
"They are killing like crazy! There's a shootout in the Lazaro Cardenas neighborhood. Steer clear of that area," read a warning tweeted by a writer in the northern city of Monterrey, the country's industrial heart now beset by drug violence.
Monterrey, which has found itself caught in the crossfire in a turf war between the Zetas and the Gulf cartel, is just one city where reporting on drug crime is moving to social media.
Analysts from Microsoft.com, led by Mexican researcher Andres Monroy Hernandez, followed for 16 months the Twitter activity of people in Monterrey, Reynosa, Saltillo and Veracruz—all cities heavily affected by drug cartels.
Their report, "The New War Correspondents: The rise of civic media curation in urban warfare," noted a prevalence of words like "bomb blasts," "gunshots" and "gunmen" on the microblogging site between August 2010 and November 2011.
Just one-third of Mexicans have access to the Internet, and only 20 percent of them write daily on Twitter.
But in the four cities studied by Microsoft.com, there are "twice as many retweets" than in US cities like Seattle, Monroy Hernandez told AFP.
The study found that the day with the heaviest Twitter activity was on August 25, 2011, when alleged members of the Zetas torched the Casino Royale of Monterrey, leaving 52 people dead. Pictures from the deadly attack and names of victims were shared 7,000 times.
The analysts have identified a half dozen Twitter accounts seen as must-follow sources on the latest development in the drug war.
— Risky reporting —
From the greater safety of anonymity with no bylines, these "social media curators" spend as much as 15 hours each day gathering information about particularly horrifying acts of violence.
"They have a lot of visibility in these cities but they try to stay anonymous," said Monroy Hernandez, who interviewed the curators and found that most are ordinary citizens reporting on crime for altruistic reasons.
One curator who only gave her name as Claudia said: "It's as if I had a new beat covering social media covering the urban warfare that we are currently experiencing."
The epidemic of drug violence that has claimed more than 70,000 lives in Mexico since 2006 has made this one of the most dangerous countries for journalists.
Since 2000, 86 journalists have been killed and another 18 have gone missing, according to Mexico's Human Rights Commission.
The rise of social media reporting is a result of "the role of the press as a provider of information being hampered, the increased pressure it finds itself under, the lack of protection afforded journalists—and the dangerousness of the drug traffickers," said Octavio Islas, director of strategic digital communication at the Monterrey Institute of Technology.
Despite their efforts to stay in the shadows, some bloggers have faced the wrath of drug gangs.
A government official who works in the intelligence field said cartels have ways to access information, intercept phone calls and determine the identity of a site's administrator.
In September 2011, the decapitated body of a 39-year-old mother of two was found in Nuevo Laredo, which borders the United States.
Next to her body, police found a keyboard and a note explaining that she was killed for her online writing about organized crime.
A few days earlier, the bodies of a man and a women—both bloggers—were found hanging from a bridge in Nuevo Laredo.
The victims were correspondents "who regularly sent us information," said a woman who goes by the name Lucy and who edits "El Blog del Narco," which publishes stories, graphic photos of headless bodies and videos about the daily violence.
Lucy was forced to flee to Spain after the disappearance of her partner, who had been in charge of maintaining security for the site.
She used online posts from journalists, police, soldiers, taxi drivers, housewives and even members of the crime gangs, all of whom provided photos, videos and other documentary evidence of the heinous drug trafficking business.
Another blogger uses a Facebook page, "Valor de Tamaulipas," to report on one of Mexico's most crime-plagued states.
Crime syndicates offered nearly $47,000 for information about the blogger, but the page's administrator has refused to stop posting about crime.
Explore further: Mexican hacker group member freed by cartel: report