The GCSB is refusing to say whether private information from Gmail, Facebook and other other online accounts has been captured by United States spy bosses and whether they can access it.
United States intelligence agencies have been outed as running an interception programme called Prism which gives them direct backdoor access to some of the internet's biggest companies.
It followed the revelation of a secret court order which saw the National Security Agency collect massive amounts of information about Americans and their calls.
New Zealand is a member of the Five Eyes/Echelon network and the type of information being collected would be the sort shared with the United States' intelligence partners, according to National Security Agency whistleblower William Binny.
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By law, the bureau cannot spy on New Zealand residents or citizens. But if the information was intercepted by intelligence partners, the law is less clear.
In the Kim Dotcom case, part of the illegal surveillance saw the GCSB send the Five Eyes network "selector information" of the sort used to match the "big data" pool the NSA has been caught capturing.
The Weekend Herald asked the bureau if it had access to the information and if it included New Zealand information. It refused to comment, saying the details were "operational".
The Weekend Herald recently revealed the NSA sent a surveillance program to New Zealand called ThinThread about a decade ago. The system sucked up all "metadata" and analysed it to find patterns of behaviour authorities might find were disturbing.