"You're a hipster or from another urban tribe or trend and you say so online. But don't display all your private life. Privacy comes before being trendy." On February 25, these 140 characters gave birth to a Twitter phenomenon. The missive generated over 7,300 retweets, 1,600 favorites and hundreds of responses. The content didn't appear to be anything new; a millionth piece of advice to internet users in the slang of the medium. What was new is the identity of the issuer: the National Police. With gems like this, @policía has become the most-followed Spanish institution and the second law enforcement agency in the world, behind the FBI.

Twitter is an online henhouse where the loudest do not always triumph, but where the tone of the cluck is key. In Spain, with more than five million Twitter users, 300 retweets is considered a success. On this basis, @policía is doing well. The idea was born in 2009 as a discreet way to use new communication tools to diffuse prevention campaigns, publish police success stories and seek the cooperation of the citizenry.

A dozen officers aged around 25 with degrees in journalism, psychology or sociology manage the account. However, its director does not wear a uniform. Carlos Fernández Guerra, 39, is an expert in digital strategy and the enthusiastic community manager for the National Police.

"We're not the Official State Bulletin or a shop window for the director general

[whose office is next door]. You can't sound officious; Twitter is cruel and you can be rejected for the smallest thing. The objective is to reach the citizen who uses the web and provide a service. In this case, warning about the danger of publishing personal details. We use the language of our followers. We imitate them, we learn from them; we are a living account."

The 1,000 mentions, 300 questions and 100 answers generated each day by four or five tweets show the interest in the account. @policía doesn't only publish advice and warnings, but also serious content dealing with cyber bullying, fraud, gender violence, bullying at school or drug abuse. It also responds to followers. In private messages people can make a police complaint or ask a question and be referred to the relevant department.

Inspector Carolina González, a member of the team, says that operational results come about through the account. "On the TuitRedadas side we organize we receive thousands of messages with clues. Through one, we arrested nine Dominicans carrying 277 kilos of cocaine hidden between cattle skins in a truck." Online grasses? "Citizen cooperation."

Others are not so obliging: "These are the same people that hit me in the ribs with a nightstick," was one reply to the hipsters tweet. "Of course we get trolls, most of all at night. Don't forget we're the police. The negative response is one percent. If we get to three I'll start to worry," says Fernández. But most are positive: "You're the best"; "You couldn't be funnier"; "You're the best fake account on Twitter."

However, even the guru can imitate the pupil. Fernández regrets posting a personal message about a program called Who wants to marry my son? through @policía. Comedian Eva Hache tweeted: "What is the police doing tweeting about @uglykids?"

"We're human," admits Fernández.