Snowden, who is residing in Russia, provided UK media with top secret NSA files in 2013 revealing that the online spy agency was covertly sifting through communications of millions in the United States and abroad.
"Snowden seems to have plundered the NSA like no one else ever plundered a US intelligence agency before," Maassen speculated during a closed parliament hearing on Thursday.
Maassen said Snowden’s revelations, which include papers showing how the NSA had intercepted communications of German security agencies, had driven a wedge between Washington and its key allies in Berlin.
Snowden mocked the security chief on Twitter for making claims about his links to Russia’s Foreign Intelligence Service (SVR) or its domestic Federal Security Bureau (FSB), saying "there is currently no evidence that Maassen is an SVR or FSB agent."
Snowden previously refuted allegations he cooperated with Russian agencies. This was also denied by President Vladimir Putin who said the country’s intelligence services had never worked or were working with the former NSA contractor.