http://www.businessinsider.com/linknyc-takes-web-browsing-away-from-wifi-hubs-2016-9DNAInfo previously reported that people were using the hubs to watch porn ...
I guess that explains what substance was used to pen graffiti on the mailbox drop. There were 400 of these devices scattered across NYC, all on the street in plain view. NY residence must be pretty brazen to watch porn among passersby, then shoot their wad on the curb if penning graffiti is not their cup of tea.