IRSF is a fascinating topic. As it was explained to me (anyone feel free to correct me if I'm wrong), a shady/criminal organization takes control of a piece of

IRSF is a fascinating topic. As it was explained to me (anyone feel free to correct me if I'm wrong), a shady/criminal organization takes control of a piece of the phone network. They pick a range a phone numbers for a country that is usually expensive to call, maybe a range of numbers that doesn't actually exist in that country, and they use the phone network to "advertise" a slightly cheaper route to connect phone calls to those numbers. Instead if it costing $1, it costs $0.80. When someone makes a call to those numbers, they charge the cheaper rate, and then don't actually connect them to a real phone. Every time a call is made, they just get money. The "S" is for "shared". They offer other organizations "for every call you generate to this range of numbers, we give you a cut". Let's call it 20 cents. Now picture how many organizations are vulnerable to this. Every "call me back when a customer service rep is available". Every "call me to let me type in a code to verify I'm human". Every "leave a number our sales team can reach you at". They're all being attacked by these sorts of things constantly. The cost to get a bot to trick the system into making a phone call is much smaller than the revenue generated. As long as that is true, the attacker wins.