It doesn't take much to find a child Presto card for sale online — a quick search turned up almost 10 ads. And finding a seller isn't hard either.

In recent days, CBC News has been examining how easy it is for adults to get their hands on Child Presto cards, which allow them to board TTC vehicles for free.

The TTC says adults using those cards are costing it millions in lost fares every year. But beyond flagging illicit listings to online retailers, the transit agency says there's not much that can be done.

Farrah Merali investigated: