US forces have debated over cutting internet access to parts of Syria. Picture: Getty Images.

Cyber Command — better known as CYBERCOM — officially started attacking the tech-savvy IS group in April, in what was the command’s most important offensive since being established in 2010.

Thomas Atkin, the acting assistant defence secretary for homeland defence and global security, said a “careful balance” needed to be struck, when asked why the military does not simply stop jihadists from accessing the internet.

“It’s a careful balance, even in Raqa or Mosul (in Iraq), or anywhere on how we balance the rights to have access to the internet versus the use of the internet illegally by folks like ISIL,” Mr Atkin told the House Armed Services Committee, using an IS acronym.

Officials said the IS group’s online use was a source of valuable intelligence, but Republican committee chairman Mac Thornberry expressed concern Mr Atkin was arguing Raqa citizens have “some sort of inherent right” to access the internet.

The jihadists have used their social media savvy to deliver propaganda and disseminate their vision for a so-called caliphate across parts of the Middle East.

Though Pentagon chief Ashton Carter has frequently touted CYBERCOM’s offensive against the IS group, most details remain classified.

CYBERCOM deputy leader Lieutenant General Kevin McLaughlin said the Pentagon had gained important experience fighting the IS group online.

“It’s given us the opportunity to learn and mature and kind of plough back in lessons learned in a real circumstance that it might have taken us several years to learn,” Mr McLaughlin told politicians.

According to the New York Times, CYBERCOM has placed “implants” in IS networks that let experts monitor the group’s behaviour and ultimately imitate or alter commanders’ messages so they unwittingly direct fighters to areas likely to be hit by drone or plane strikes.

Another technique likely being employed is a common type of cyber attack known as a denial of service.

In a sign of the strategic importance virtual warfare now plays, politicians said it was time for CYBERCOM to stand up as its own combatant command — an organisational super structure normally arranged along geographic boundaries.

CYBERCOM has about 4700 troops, but is set to expand to 6200 in 2018.