The designers of Stuxnet, the computer worm that was used to vandalize an Iranian nuclear site, may have struck again, security researchers say.

Stuxnet, which infected tens of thousands of computers in 155 countries last year, created an international sensation when experts reported that it was designed as an American-Israeli project to sabotage Siemens Corporation computers used in uranium enrichment at the Natanz site.

The researchers say the new malicious program, which they call Duqu, is intended to steal digital information that may be needed to mount another Stuxnet-like attack.

The researchers, at Symantec, announced the discovery on the company’s Web site on Tuesday, saying they had determined that the new program was written by programmers who must have had access to Stuxnet’s source code, the original programming instructions.