Pornography is no longer the leading source of malware on mobile devices, according to a new study.
The non-honor now goes to Web-based ads, according to Blue Coat, a security firm that analyzed data from more than 75 million global users for a report it released Wednesday.
As of last month, a whopping one in five mobile users who were directed to malware got there by clicking on a Web ad, Blue Coat said. That's more than triple the 5.7 percent rate logged in November 2012, when ads were the No. 4 delivery system of mobile malware.
"Being in the security space, we're not often surprised by these stats -- but that is a big jump in a short period," said Sasi Murthy, the vice president of product marketing security for Blue Coat.
Still, the rise of malicious ads doesn't mean it's safe to view risqué content on mobile devices. Porn is still the most efficient method of malware delivery, Murthy pointed out.
Porn viewing makes up only 1 percent of mobile browsing activity, but it accounts for 16 percent of all malicious attacks. Web ads, by comparison, comprise 12 percent of requested mobile content and 20 percent of attacks.
The February 2014 data represents a big shift from Blue Coat's November 2012 figures. At that time, porn was the No. 1 delivery system of mobile malware, at more than 22 percent. That category slipped to No. 3 in last month's rankings, driving users to malware 16 percent of the time.
The upward trend in malicious Web ads is concerning for a few reasons, Blue Coat said. First, the "malvertising" is delivered through the same networks as legitimate ads. Meanwhile, the amount of legitimate ads is also increasing — which makes it even more confusing for users to tell which content may be malicious.
It makes sense that scammers are targeting ad channels, Blue Coat said, because people use their mobile devices for "recreational" activities like shopping and entertainment nearly 12 percent of the time. That's prime content for ads.
"[Scammers] work like a business," said Murthy. "They're focused on low investment and high return, so they will go where the activity is."
Blue Coat's full 10-page report includes data on other mobile threats and suggestions for staying safe, including:
- Avoid clicking on ads on mobile devices.
- Avoid pornography on mobile.
- Consider blocking Web ads as a content category altogether.
- Never download an app outside of legitimate marketplaces like the Apple App Store or Google Play.
