An audacious attack on Iran's nuclear programme may have backfired and made its security stronger.
The Stuxnet virus was a highly sophisticated cyber attack, which in 2009 and 2010 infected uranium enrichment centres at Natanz in Iran.
It targeted industrial control systems which separate uranium, and at the time was said to have been a potentially game-changing setback for the regime.
But while the virus may still have damaged production in the short term, a new report claims that its wider impact is still unclear.
The report by Ivanka Barzashka for the Royal United Services Institute for Defence & Security Studies, it is argued that evidence of its effects are mostly circumstantial.
While calculations of the potential impact of Stuxnet were dramatic, independent analysis is unable to confirm it, the report said:
"Stuxnet's effects have not simply worn off: Stuxnet was never very successful from the start. If the purpose of the malware was to decrease Iranian nuclear-weapons potential, it clearly failed."
"Iran's ability to install and operate new IR-1 centrifuges was not seriously hindered, as it began production of uranium enriched to 20 per cent in February 2010 - a development which significantly increases its weapons potential."
It is argued that data collected by the International Atomic Energy Agency shows Iran has been able to "progress quietly" with enriching uranium.
However the report has also been criticised by some, including former foreign secretary Sir Malcolm Rifkind, who told the Telegraph that it "is undoubted is that it [Stuxnet] significantly slowed down the enrichment process".
It is not known for sure who was behind the attack, though according to the New York Times officials commenting under anonymity have admitted the United States and/or Israel may have been involved.