Spam might no longer be the gigantic server overhead it once was but the number of unsolicited messages containing malicious links appears to be surging, according to figures from SaaS security firm ProofPoint.

And quite a surge it is, with stats drawn from its own filtering systems showing that in the 210 days of 2014 up to 29 July, the percentage of unsolicited emails containing malicious links exceeded 15 percent on 63 days.

This means that around one in six messages were malicious, with this rising to one in four on 12 days, and one in three on two days.

“This is unlikely to be a temporary phenomenon, as spam authors move to take advantage of the greater accessibility and profitability of malware,” said its research blog.

If spam was a huge traffic-generation con, malicious links now lead to more profitable schemes, it said.

“Compromised computers create many revenue opportunities for phishers, who can sell them for bitcoin mining, click-fraud, spam distribution, and other services.”

As Palo Alto Networks reported a few weeks ago, even the social engineering kings, Nigerian 419 scammers, are at it. Where once they sent pleading emails by the billion, they are now as likely to use malware links in the same emails.

Interestingly, ProofPoint believes that spam has been creeping back up in 2014, reaching towards the peak levels of 2010 with 260 billion processed per day during July. Other firms including Cisco have noticed rising volumes although Trend Micro’s figures suggest a lot of volatility.

That suggests that the effectiveness of the botnet ‘takedowns’ of 2011 onwards is starting to wane. Spam might be making a return but we are a long way from the unstoppable deluge of a few years back.

But the absolute levels could now be beside the point. Malware distribution is no longer a sideline for spammers but the core business model. It is not about volume but clicks.

The firm’s recommendation is a pretty radical one – treat all unsolicited email as suspicious.  That sounds like a simple prescription but it is anything but because email thrives on new contacts.

“Unwanted email can no longer be simply regarded as a nuisance: every single unwanted email that gets through an organization’s filters can carry a malicious link, even as the enabling technology of multi-variant phishing campaigns makes it more difficult to distinguish the 15 percent, 20 percent or even 30 percent of links that are malicious from the rest.”