“A Court-wide impact analysis is being carried out, and steps are already being taken to mitigate any effects of the incident,” the court said in a statement.
The attack happened last week.
“All necessary measures have been taken to ensure the business continuity,” court spokesman Fadi El Abdallah told The Associated Press.
The incident happened in the same week that The Hague hosted a summit of 32 NATO leaders at a conference center near the court amid tight security including measures to guard against cyberattacks.
The court declined to say whether any confidential information had been compromised.
The ICC has a number of high-profile investigations and preliminary inquiries underway in nations around the world and has in the past been the target of espionage.
In 2022, a Dutch intelligence agency said it had foiled a plot by a Russian spy using a false Brazilian identity to work as an intern at the court, which is investigating allegations of Russian war crimes in Ukraine and has issued a war crimes arrest warrant for President Vladimir Putin, accusing him of personal responsibility for the abductions of children from Ukraine.
Arrest warrants for Israeli Prime Minister Benjamin Netanyahu and his former defense minister, Yoav Gallant, over Israel's campaign against Hamas in Gaza have also drawn ire. U.S. President Donald Trump slapped sanctions on its chief prosecutor, Karim Khan, in February and earlier this month also sanctioned four judges at the court.
The court is still feeling the effects of the last cyberattack, with wifi still not completely restored to its purpose-built headquarters.