The Iranian government says it has discovered a second computer worm specifically designed to target its IT systems.

Authorities did not reveal which systems were targetted by the worm, dubbed Stars, but they did say "that the damage is very slight in the initial stage".

Last year, a worm called Stuxnet was found to have infiltrated control systems at an Iranian nuclear facility.

The director of Iran’s Passive Defense Organisation, Gholam-Reza Jalali, last week explicitly accused the US and Israel of involvement in Stuxnet. "The investigations show the source of the Stuxnet virus originated in America and the Zionist regime," said Jalali said, according to an Iranian newspaper.

At the time, he accused German engineering giant Siemens, whose control systems the Stuxnet worm targets, of corroborating with Iran’s enemies."The Siemens company must be held accountable and explain how and why it provided the enemies with the information about the codes of [control system] software and paved the way for a cyber attack against us."
 
In his announcement about the Stars worm, Jalali said Iran might be able take legal action against the US and Israel for their alleged involvement in Stuxnet.

“The Foreign Ministry might not have paid due attention to pursuing this issue legally," local, pro-government news agency MehrNews quotes Jalali as saying. "But it seems that our diplomatic apparatus should pay attention to legally pursuing cyber attacks against the Islamic Republic of Iran more than before, since many countries, such as Russia, regard any cyber attack as an official (act of) war.”
    
Iran is not alone in suspecting US and Israeli involvement in Stuxnet. Earlier this year, German control systems security analyst said that he suspected that Israeli intelligence agency Mossad was involved in the creation of the virus, but added that the US was the "leading source".

However, there is only circumstantial evidence to back this claim.