However the overall figures are small: 12,000 phishing attempts were blocked each day while there were 300 hits per day for Web exploits, both cases referring to malicious code delivered over secure connections.
The figures were derived from a study done by the company's ThreatLabZ and found that an average of 60% of transactions in the Zscaler security cloud were delivered over SSL/TLS.
The numbers are based on Zscaler customers who use the SSL inspection feature.
"Hackers are increasingly using SSL to conceal device infections, shroud data exfiltration and hide botnet command and control communications,"said Deepen Desai, senior director, security research and operations.
"In fact, our study found that the amount of phishing attempts per day delivered over SSL/TLS has increased 400% from 2016."