Iran said on Sunday it had detected Duqu, a computer virus that experts say is based on Stuxnet, the virus that hit the Islamic Republic’s computers last year.

“We are in the initial phase of fighting the Duqu virus,” Gholamreza Jalali, the head of Iran’s civil defense organization, told the official IRNA news agency. “The final report which says which organizations the virus has spread to and what its impacts are has not been completed yet.”

He added, “All the organizations and centers that could be susceptible to being contaminated are being controlled.”

According to the Reuters news agency, news of Duqu surfaced in October when security software maker Symantec Corp said it had found a mysterious virus that contained code similar to Stuxnet.

Duqu appeared to be designed to gather data to make it easier to launch future cyber attacks, experts told Reuters. Stuxnet was aimed at crippling industrial control systems and may have destroyed some of the centrifuges Iran uses to enrich uranium.

After Stuxnet targeted Iran’s nuclear facilities and other industrial sites last year, the Islamic Republic acknowledged that it had affected a limited number of centrifuges at its main uranium enrichment facility in the central city of Natanz. However, it claimed its scientists discovered and neutralized the malware before it could cause serious damage.

In April, Iran said its nuclear program had once again been attacked, this time by a different computer virus called Stars.

The Stuxnet attack is widely believed to have been an Israeli cyber-attack, but Israel has not admitted it.

The attempted Duqu attack was announced just one day after a mysterious blast at a missile base southwest of Tehran.

17 people were killed in the explosion, including a senior Iranian Revolutionary Guards missile expert.