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  One investigative record showed DHS used administrative subpoenas to obtain “wire transfers from various financial institutions to and from” SEIU, one of the largest unions in the US. Investigators also requested that the Federal Reserve Bank of New York provide financial data from the Communications Workers of America, an international union, the records showed.

The attendance was clandestine and performed by actors that misrepresented themselves to gain an intelligence advantage. I'm not sure what else you would call it.

> If the meetings are open to the public then anyone can attend (i.e., "spy") on them.

It’s the systematic, motivated, and targeted collection of data that makes it spying. When the KGB takes photos of licence plates of people leaving a military base, we call it “spying”. Replace this with Homeland Security and a neighborhood organizing meeting.