Airbnb, the pioneering home rental service, presents itself as useful and virtuous, but the reality is far less benign, according to a report that Eric T. Schneiderman, the New York attorney general, released on Thursday.

The report will say nearly three-quarters of all Airbnb rentals in the city are illegal, violating zoning or other laws. Commercial operators, not hard-luck residents, supply more than a third of the units and generate more than a third of the revenue. At least a handful of landlords are running what amount to illegal hostels.

Property owners on Airbnb are indeed making money, but it is not being spread around. Most rentals are in three high-profile Manhattan neighborhoods. Queens, the Bronx and Staten Island barely figure.

Airbnb declined to aggressively dispute the numbers in the report, which draws on four years of data it provided to the attorney general after a court fight.