The European Parliament building in Brussels, Belgium.
CNN  — 

Right-wing populists are set to make unprecedented gains in the elections to the European Parliament taking place next month. As European officials brace for a new-look parliament, there are growing concerns that the 27-nation bloc could become more vulnerable to adversarial states seeking to do the union harm.

Polling data suggests that far-right Members of the European Parliament (MEPs) could have enough seats to, together, block the passage of European Union legislation, creating a massive headache for the union as a whole.

As important as this shift may become in influencing the most powerful people in Brussels and the direction of the bloc, officials are now concerned about the impact this will have on the EU’s security.

The recent arrest of a German national working as an aide to a far-right MEP on suspicion of spying for China has fueled fears that a substantial influx of Euroskeptic, anti-establishment figures who have lived lives on the fringes of mainstream politics will mean a lot of sitting ducks for adversarial states to target.

European Commission President Ursula von der Leyen speaks as she attends a press conference at the Zenon Joint Rescue Coordination Center in Larnaca, Cyprus, on March 8.

“Elected populists are uniquely attractive to malign actors for two reasons,” said James Shires, co-director of the European Cyber Conflict Research Initiative.

“First, they are anti-establishment figures who don’t trust the institutions or structures they now work inside. It is hard to make the jump from believing there is an establishment conspiracy against you to cooperating with those institutions to counter security threats,” he said. “Second, in many cases, there is instinctive alignment with states like China or Russia. They agree with them in certain areas and are happy to put forward views, and even spread misinformation, on their behalf.”

While hostile actors attempting to influence politicians is hardly new, an influx of populists to an institution like the European Parliament at this precise moment in time is particularly concerning.

One point European security officials make is that these smaller, newer parties don’t have much experience of working with security services, or even have much experience — or indeed interest — in vetting their own candidates or staffers.

The European Parliament itself does not have a unit set up to screen parliamentarians and relies on the 27 EU member states who send MEPs to Brussels and Strasbourg.

“For some countries, that is a six-month process, in others it can take two years,” a senior European Parliament source told CNN. “Large parts of the EU treaties don’t apply to security services, so we have very little central oversight and countries are not obliged to send us sensitive information. We can do criminal record checks but, you’ll be shocked to learn, most spies don’t have active criminal records.”

What damage could an MEP actually do once elected to the European Parliament? There are multiple opportunities to wreak havoc from inside the system, but two in particular stand out.

Nigel Farage, former leader of the UK Independence Party, listens to speeches at the European Parliament on Wednesday, April 5. The parliament was debating "Brexit" -- the UK's decision to leave the European Union.

The first is more innocuous on the surface. MEPs are allowed to make speeches in parliament that are recorded, clipped and promoted on social media. Many British former MEPs used these speeches to great effect between 2010 and 2016 as a way of spreading Euroskepticism in Britain. This ultimately played into Britain’s departure from the EU.

If MEPs want to stand up and spread misinformation or disinformation that aligns with the objectives of states who are hostile to the EU, they are perfectly entitled to do so. They can stand up and denounce Europe’s support for Ukraine, rail against equal marriage and climate change, all to undermine Western ideas and sow disunity. Knowingly or unknowingly, it doesn’t matter: If it aligns with the interests of a hostile state, it aligns with the interests of a hostile state.

This is difficult for the EU because, unless an MEP is being paid directly by a foreign state to lobby and lie on its behalf, it’s perfectly legal.

“One can be ‘Putinist’, or ‘Xi’st’, and that is OK — in the sense that they have a right to their opinion. It only becomes an issue if they are working with foreign powers to advance their agenda,” an EU security source told CNN. “Otherwise, it is democratically legitimate for them to have an opinion and express it in the Parliament.”

The second major way an MEP or member of their staff could hurt the EU to the benefit of a hostile state is through illegal means. Leaking sensitive information to which they have access, aiding in cyberattacks, stealing documents and handing them over to foreign actors – what is considered more classic espionage.

Between the 27 member states — all of whom have embassies, multiple institutions, hundreds of elected officials and thousands of members of staff — Brussels is a place where lots of sensitive information is flying around. Quite a bit of it gets leaked.

Anything from future EU plans to the personal details of individuals could be valuable to those who wish to do the EU harm. One senior EU diplomat told CNN that this was of particular concern now that Europe is taking more serious and direct action in security and defense policy in response to Russia’s full-scale invasion of Ukraine in 2022.

With Brussels seeking to be taken ever more seriously as a diplomatic player, its own security will come under increasing pressure from international rivals. Whether it takes sufficient measures to stop those who want to do it harm rests solely with the EU and its member states. And failure to do so could scupper those grand ambitions of greater global relevance.