SAN FRANCISCO — It took Facebook seven years to raise $1 billion from investors. Uber did it in five.

The messaging company Telegram has been around since 2013, but never tried to raise significant money until late last year. Now, thanks to an initial coin offering, or I.C.O., Telegram is on track to pull in a billion dollars in just four months — long before the product the company is raising money for is even built.

When programmers or entrepreneurs launch an I.C.O., what they are really doing is selling their own virtual currencies in order to raise money for software they say they are building. In return for real money, investors receive digital tokens, similar to Bitcoin.

Regulators worry this novel fund-raising method is allowing people to flout the rules that are supposed to protect investors. Financial authorities around the world have been promising to crack down on coin offerings, which rose out of nowhere last year to become a popular way for start-ups to raise tens of millions of dollars, sometimes in minutes.