The European police agency Europol will target the estimated 40,000 to 50,000 accounts linked to the terrorist organisation.
Working with unnamed social media companies, it aims to shut down the accounts within two hours of them being discovered.
Calls for more to be done to tackle online radicalisation have mounted in recent weeks after claims that Talha Asmal, who was reported to have become Britain’s youngest suicide bomber, was groomed over the internet.
Talha, 17, is alleged to have fled his home in Dewsbury, West Yorkshire, in March to join IS and reportedly detonated a vehicle while fighting for the group in Iraq.
His family said he had been exploited by extremists on the internet “in a process of deliberate and calculated grooming”.
Rob Wainwright, Europol’s director, said the new unit, which comes into force on July 1, would work to identify the key accounts being run in a number of languages that “underpin” what IS is doing and would aim to “identify the ringleaders online”.
He told the Guardian it would also monitor social media to identify any activity targeting people who might be vulnerable, as well as those preying on them.
He said: “Who is it reaching out to young people, in particular, by social media, to get them to come, in the first place? It’s very difficult because of the dynamic nature of social media.”
Mr Wainwright added that money used to fund IS would be tracked down, saying: “Where you follow the money trail, it helps find who they are, what they are doing and who their associates are.”
Europol believes up to 5,000 people from the EU, including those from the UK, France, Belgium and the Netherlands, have travelled to IS-held areas.
Around 700 Britons are thought to have travelled to IS-controlled regions of Syria and Iraq.
The former reviewer of anti-terrorism legislation, Lord Carlile, has called on the government to work with computer programmers and social media companies to counter extremist propaganda online.
Mr Wainwright said that IS had proved to be “very technologically adept” and had exploited the internet and social media in a much bigger way than other terrorist organisations had in the past. “We will have to combine what we see online with our own intelligence that is shared with us by European police services so, therefore, we can be a bit more targeted, identifying who the key user accounts are and concentrating on closing them down and then pursuing the more conventional counter-terrorism investigation around them,” he said. “So in the end what we are hoping to have is strategic impact against the problem as a whole rather than just playing a simple numbers game.”
Meanwhile Keith Vaz, chairman of the Commons home affairs committee, yesterday said that the UK needs to “sharpen up our act” when it comes to contacting Turkish authorities. He was speaking after meeting the “heartbroken” husbands of two of the three sisters feared to have travelled to Syria with their nine children.
British sisters Khadija Dawood, 30, Sugra Dawood, 34, and Zohra Dawood, 33, and their children, aged between three and 15, are feared to have travelled to link up with terror group Islamic State.