Ransomware dropped to less than 1% of email-borne payloads while remote access trojans increased to 4%. The company claims to analyse five billion emails every day, apart from about social media posts and 250 million malware samples.

Most of the malware that arrived was linked off URLs in email, rather than arriving as attachments, the report found, adding that phishing of corporate credentials grew by more than 300% between the second and third quarters of the year.

Web-based threats were mostly social engineering attempts, with fake anti-virus and bogus plug-ins appearing at twice the frequency as in the second quarter.

Social media platforms had become more efficient at blocking phishing links, the report said, with a 90% decrease in links compared to the corresponding quarter in 2017.

But social media support fraud had grown, reaching the highest level recorded by Proofpoint, in September.

The company said it recommended the following:

"Assume users will click. Social engineering is increasingly the most popular way to launch email attacks, and criminals continue to find new ways to exploit the human factor.

"Leverage a solution that identifies and quarantines both inbound email threats targeting employees and outbound threats targeting customers before they reach the inbox.

"Build a robust email fraud defence. Highly targeted, low-volume email fraud attacks often have no payload at all and are thus difficult to detect. Preventing email fraud requires a multilayered solution that includes email authentication and domain discovery, as well as dynamic classification that can analyse the content and context of emails, stopping display-name and lookalike-domain spoofing at the email gateway.

"Protect your brand reputation and customers. Fight attacks targeting your customers over social media, email, and mobile—especially fraudulent accounts that piggyback on your brand. Look for a comprehensive social media security solution that scans all social networks and reports fraudulent activity."