Der Spiegel claims source code has linked attack to Russia.
Russia is under suspicion for allegedly backing a cyberattack on the German Bundestag, in only the latest example of online war between major powers.
An analysis of spyware involved is said to have led investigators to believe that Russia is responsible for the attack, which targeted 20,000 accounts used at the German parliament, according to sources at current affairs magazine Der Spiegel.
The malware is also said to resemble a similar program used to attack Germany last year.
Official sources refused to confirm the allegation that Russia could have been involved in the attack, though a government spokesperson did say that the parliament had been under attack for several days.
Earlier this year hackers attacked German government websites in connection with the country’s diplomatic efforts during the Ukraine crisis.
Ukraine later accused Russia of backing the attack, but responsibility for it was claimed by CyberBerkut, a hacking gang modelled on the Anonymous movement that has no ostensible link to any government but is hostile to Ukraine’s government.
Recently CyberBerkut accused the US of suppressing information on Ukrainian violation of ceasefire agreements signed in Minsk by both Ukraine and Russia, dumping alleged satellite images of weapons being deployed in contravention of the deal.
Cyberattacks backed surreptitiously by countries appear to have been on the rise recently, with governments such as Russia and China widely suspected of using hacking gangs to distance themselves from the attacks.
Most infamously the hit on Sony last year was attributed to North Korea, with the US government and security expert Bruce Schneier linking the Asian regime to the attack.
However prior to that the US and Israel are thought to have backed an attack on Iran’s nuclear infrastructure by sponsoring development of the Stuxnet virus, which destroyed nuclear centrifuges.