We're not making any moral judgments here. But it is definitively a bad idea to visit pornography sites on your smartphone or tablet.

Nearly one-quarter of malware on mobile devices comes from porn websites, according to a new study from Blue Coat, a Web security and optimization company.

Mobile users don't check out porn sites often -- less than 1% of all mobile traffic is pornography. But when they do go to those sites, the risk of inadvertently downloading malware to their devices increases three-fold. That makes watching porn on smartphones a far bigger threat than viewing porn on a PC.

Porn led to more malware on smartphones and tablets than e-mail spam, malicious websites, and fake apps combined.

Part of the problem, Blue Coat said, is that the nature of mobile devices makes differentiating legitimate sites from malicious ones a tricky task. There is no way to hover over shortened URLs to reveal their true destination, for example.

"No matter how tantalizing a link might look on a desktop, there are cues that you shouldn't go there, such as an address that just doesn't look safe," said Hugh Thompson, chief security strategist for Blue Coat. "When you click a link on a mobile phone, it's harder to know what form of Russian roulette they're playing."

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Porn is a leading traffic driver on the Internet, and for many years, porn sites had been a primary source of malware on PCs as well.

"When you delve into the world of online pornography, you don't often know where you are, or where the content is coming from," said Thompson. "But when you're visiting those sites, you are more inclined to make riskier choices than elsewhere on the Web."

But cyberattackers are increasingly finding new ways to target an even larger audience, including phishing, uploading malicious advertisements and poisoning search engine results.

Security experts predict that broader-based cybercrime schemes are likely to appear on smartphones and tablets soon. For now though, mobile attacks appear to be mirroring techniques used on traditional computers.

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Still, major security firms have widely predicted that this will be the year mobile devices will finally emerge as a major target for cybercriminals. Smartphones have become personal computers that travel around with us at all times, and the vast majority of users don't even lock them with a password.

Cyberthieves continue to make so much money attacking Windows PCs that there hasn't been much incentive to change tactics. But we're about to hit a tipping point. Most people still do their online banking and shopping on their PCs, but those transactions are happening on mobile phones more frequently.

According to research from Juniper Networks (JNPR), 300 million smartphones around the world will be equipped with the near-field communications (NFC) chips needed for mobile payments this year. Juniper also predicts global NFC transactions will total nearly $50 billion.