Google is the latest company to crack down on advertising for cryptocurrencies.

The search giant said Tuesday it will revise its ad policies in June to restrict ads for cryptocurrencies and related information, such as initial coin offerings, cryptocurrency exchanges and wallets and cryptocurrency trading advice. That ban goes for both ads on Google's own website and sites Google serves on other sites.

The ban is another big blow for the nascent market of digital coins, with Facebook in January banning crypto ads, too. That means young crypto businesses and exchanges will be barred from advertising on the two biggest online ad platforms. Google and Facebook were expected to gobble up 63 percent of US digital ad spending last year, according to eMarketer.

Google's ban comes as bitcoin and other cryptocurrencies still struggle with fraudulent activity and illegal transactions, such as one ICO from the startup Prodeum that apparently resulted in the company taking off with investors' money. Because digital coin exchanges are still largely unregulated and transactions are hard to reverse, they've become targets for scams and hacks.

"We don't have a crystal ball to know where the future is going to go with cryptocurrencies," Spencer Scott, Google's director of sustainable ads, told CNBC, "but we've seen enough consumer harm or potential for consumer harm that it's an area that we want to approach with extreme caution."

The top 10 digital currencies by market cap, except NEM, were trading lower early Wednesday, according to the site CoinMarketCap.

Advertising is Google's lifeblood, but the company knows its business is hurt by ads that lead to scams or malware. In 2017, Google removed 3.2 billion bad ads, nearly double the 1.7 billion it removed in 2016.

First published March 14, 9:32 a.m. PT.
Update, 10:27 a.m.: Adds background about Google's effort to eliminate bad ads.