BRUSSELS, Belgium - The EU on Monday announced "formal infringement proceedings" against Elon Musk's X platform under a law cracking down on illegal online content, after identifying disinformation related to Hamas's October 7 attack in Israel.

The action against the company formerly known as Twitter is the first against a major online platform since Brussels implemented the Digital Services Act (DSA), a sweeping piece of European Union legislation that strengthens online companies' responsibility for content moderation.

"Today’s opening of formal proceedings against X makes it clear that, with the DSA, the time of big online platforms behaving like they are 'too big to care' has come to an end," said the bloc's digital enforcer, EU commissioner Thierry Breton.

"We will now start an in-depth investigation of X's compliance with the DSA obligations concerning countering the dissemination and amplification of illegal content and disinformation in the EU, transparency of the platforms and design of the user interface."

The European Commission said a preliminary information-gathering investigation it launched against X in October, which included looking at "the dissemination of illegal content in the context of Hamas’ terrorist attacks against Israel", led to Monday's probe.

On the basis of that information, "the Commission has decided to open formal infringement proceedings against X under the Digital Services Act", it said.

The formal probe will examine four areas: the dissemination of illegal content; the effectiveness of X's efforts to combat disinformation; suspected restrictions on giving researchers access to its data; and suspected deceptive practices -- known as "dark patterns" -- related to its Blue Tick subscription product.

In the event of proven infringements, the DSA carries penalties that can include fines going up to six percent of an online company's global revenues.

For serious and repeated violations, the EU can ban a platform operating in the 27-nation bloc.

Disinformation 

The commission said that, under the formal probe against X, it would now "continue to gather evidence, for example by sending additional requests for information, conducting interviews or inspections".

It noted that the proceedings gave it powers to order X to undertake interim or remedial steps, pending the conclusion of the probe.

There is no deadline for the proceedings to wrap up.

Weeks after starting its initial information-gathering exercise against X, the commission also launched preliminary investigations along the same lines against TikTok, YouTube and Facebook owner Meta.

Those investigations also looked at how the platforms handled disinformation and illegal content related to the Hamas attack.

The Hamas attack on October 7 killed around 1,140 people in Israel, most of them civilians, and took an estimated 240 people hostage, according to updated Israeli figures.

Israel retaliated with an intense bombardment of the Gaza Strip, which is controlled by Hamas.

More than 18,800 Palestinians -- around 70 percent of them women, young children and adolescents -- have been killed in the Gaza Strip in Israeli bombardments since October 7, according to the Hamas government's health ministry, and much of the besieged territory has been reduced to rubble.