PARIS — A new and highly virulent outbreak of data-scrambling software caused disruption across the world Tuesday. Following a similar attack in May , the fresh assault paralyzed some hospitals, government offices and major multinational corporations in a dramatic demonstration of how easily malicious programs can bring daily life to a halt.

Ukraine and other parts of Europe were hit particularly hard by the new strain of ransomware — malicious software that locks up computer files with all-but-unbreakable encryption and then demands a ransom for its release. As the malware began to spread across the United States, it affected companies such as the drugmaker Merck and Mondelez International, the owner of food brands such as Oreo and Nabisco. But its pace appeared to slow as the day wore on.

The origins of the malware remain unclear. Researchers picking the program apart found evidence its creators had borrowed from leaked National Security Agency code, raising the possibility that the digital havoc had spread using U.S. taxpayer-funded tools.

“The virus is spreading all over Europe and I’m afraid it can harm the whole world,” said Victor Zhora, the chief executive of Infosafe IT in Kiev, where reports of the malicious software first emerged earlier on Tuesday.