There’s no reason to believe in what the German security stated. No human investigator and nobody in the Russian Federation has access to the results of the German investigation that prove Russian hacking of the Bundestag.
Unsubstantiated claims obfuscating Russia's responsibility for cyber attacks on the German Parliament in 2015. The German domestic intelligence agency said Russia was behind a series of attacks on German state computer systems, including the German parliament in 2015. According to the reports from the German media, the federal prosecutor's office has issued an international arrest warrant against Dmitriy Badin, a hacker reportedly working for the Russian military intelligence service, in relation to the cyber attack. Read similar cases here: "Accusations against Russia of hacking the Bundestag follow the same pattern as accusations over the Salisbury poisoning", "Germany accused Russia of hacking the Bundestag either to advance the Nordstream 2 or as a pretext not to participate in the Victory parade".