Researchers at Sandia National Laboratories in Livermore, Calif., are creating what is in effect a vast digital petri dish able to hold one million operating systems at once in an effort to study the behavior of rogue programs known as botnets.

Botnets are used extensively by malicious computer hackers to steal computing power from Internet-connected computers. The hackers harness the stolen resources into a scattered but powerful computer that can be used to send spam, execute phishing scams or steal digital information. These remote-controlled “distributed computers” are difficult to observe and track.

Botnets may take over parts of tens of thousands or in some cases even millions of computers, making them among the world’s most powerful computers for some applications.

“When a forest is on fire you can fly over it, but with a cyberattack you have no clear idea of what it looks like,” said Ron Minnich, a Sandia scientist who specializes in computer security. “It’s an extremely difficult task to get a global picture.”