Islamic State, the jihadist group that once held control of large parts of Iraq and Syria, is still "very much a problem" as it continues to pump out terror content online, a European security official has said.

Julian King, the EU's commissioner for the security union, said Tuesday that, although the Islamist militant organization has suffered a drop in its global influence and presence on the ground, it continues to exploit the internet as a means of promoting its extremist ideology.

"When it comes to terrorism content online there are specific organizations, most notably but not uniquely ISIS, al-Qaeda is also trying to use the digital space," King told CNBC's Elizabeth Schulze on Tuesday at the Web Summit in Lisbon, Portugal.

ISIS was once notorious for its use of online propaganda material to persuade disenfranchised young people in the West to flee their home country to fight for its cause in the Middle East. It has also claimed responsibility for numerous terror attacks in the West.

"Now, they've suffered reversals on the ground in Iraq and Syria, but they're still producing material, they still use the internet to traffic their propaganda and their radicalizing material," King said. "So it remains very much a problem that we need to deal with today."