The volume of external network traffic decreased by 32% from 464,159 gigabytes in 2011 to 315,847 gigabytes last year.
The difference is equivalent to roughly 150,000 hours, or 17 years, of video, or about 2.5 million hours, or 285 years of music. The figures did not include traffic from data stored inside the university network.
Information technology services director Mike Harte said the decrease came after the university implemented a system which blocked websites and downloads which breached its internet usage policy.
''One of the controls implemented in the system is the blocking of peer-to-peer ... sites for students.''
These file-sharing sites were typically used for illegally downloading copyrighted material, such as movies, he said.
The reduction in traffic meant an improvement in the performance of the network for legitimate users and meant it could defer increasing the capacity of its network, saving the university money.
Part of the reason why the university had cracked down on illegal downloading was because of the Copyright (Infringing File Sharing) Amendment Act, which came into force in 2011.
That law allowed copyright owners to send evidence of alleged copyright infringements to internet service providers and internet users could be fined up to $15,000 if they ignored warnings to stop the activity.
''The university treats copyright infringement very seriously and has a formal procedure in place for handling complaints about a potential copyright infringement,'' Mr Harte said.
He could not say exactly how much of the reduction in data traffic was due to fewer illegal downloads, as the university did not monitor the purpose of download traffic.
