As cryptocurrencies have gained popularity, they've also attracted additional scrutiny. In the US, for example, the Securities and Exchange Commission created a Cyber Unit focused on online financial crimes, began looking into companies that shifted their interests to crypto or blockchain, issued a number of subpoenas and brought charges against multiple firms for alleged cryptocurrency fraud. Other countries, like China and South Korea, have cracked down on digital currencies as well.

In June, Google put a new policy into place, banning ads that promote cryptocurrencies, crypto exchanges, initial coin offerings and wallets. Facebook put a similar ban into place in January, but has also since lifted some restrictions. Twitter has also taken measures against crypto-related ads.

Google's updated policy goes into effect next month. Advertisers will be able to apply for certification once it does.