Belgian, German, and Spanish authorities have arrested five people for forming an “active” and “dangerous” ISIS cell. Spain’s interior ministry has said that of the five people that were arrested, four were Spaniards and one was Moroccan.

As the Telegraph reports,

The group used social media, specifically a Facebook page “Islam en Español” (Islam in Spanish), which had over 32,000 followers, to glorify Isil and spread the message of the militant group that operates out of Syria and Iraq, the ministry said. Operating almost exclusively in Spanish, they are accused of commissioning attacks, radicalisation, promoting Islamist militancy and acting as go-betweens for the group in Europe [emphasis added].

The Spanish interior ministry further elaborated that these five people posed a “grave, concrete and continued threat to security in Europe.”

Islamic extremism is a severe problem, and the Spaniards are taking it seriously. Since raising its threat-level alert to the second-highest level in 2015, Spain has arrested 143 Islamist militants, with the majority of arrests occurring within Spain’s borders.

This recent arrest is more evidence that the allure of ISIS is succeeding in enchanting many Muslims all across the world. After all, this ISIS cell was operating “almost exclusively in Spanish” and managed to garner tens of thousands of supporters online.

The internet is now incontrovertibly the chief recruiting grounds of Islamic terrorism; it is also the chief means that jihadis use to disseminate their propaganda. But it is not just hardcore jihadi militants who are the problem—the equally if not more alarming problem is the sheer mass of support that jihadis and Islamists enjoy.

For example, a perusal of the Arabic web concerning the brutal murder of the Jordanian writer and political activistNahed Hattar  reveals that many commentators vociferously support his killing and those who “insult” the Islamic religion. Murders like Hattar’s should not be viewed in isolation, but as being symptomatic of a deeper problem within Islamic society.

It must be remembered that if one actually crunches the numbers up, more than 60 million Muslims the world over have favorable views towards ISIS—and ostensibly many more support Islamist ideas (like applying the death penalty to apostates, enforcing blasphemy laws, and stoning adulterers). And this is consistent with what can be observed by a quick perusal of the Arabic interwebs; one will see considerable support for ISIS and similar jihadi groups all over the internet.

Indeed, there are publically accessible Arabic PalTalk chat rooms with titles like, “Supporters of the Islamic State” that remain open for at least months. Such chat rooms also enjoy some of the largest audiences on the Arabic side of the prominent chat website.

If Twitter were to stop its aggressive campaign to shut down the accounts of jihadi militants, we would undoubtedly be seeing some of them garner tens of thousands of online supporters and sympathetic Twitter followers.

ISIS cells and their Islamist cheerleaders are aggressively using the internet to communicate with jihadis and perpetuate their Islamist zeitgeist. Intelligence agencies should therefore stringently monitor the interwebs and attempt to shut down Islamists web activity. (The latter measure should be undertaken provided that the Islamists cross the boundary of  freedom of expression and are conspiring with or providing support to Islamist terrorists).

Jihadi cells like the one mentioned above must not be allowed to openly propagate their militant ISIS-sympathetic views on social media sites to the point where they have thousands of followers. But the internet is a massive cyber reality, and its certain that many Islamist groups or posts fly under the radar of social media administrators. This underscores the importance of the imperative to “say something” if one “sees something.”