Zero-day web malware blocks have risen rapidly, says web security firm ScanSafe.
In its monthly Global Threat Report, ScanSafe said the rate of zero-day malware blocks increased in November to 26% of blocks.
The number increased significantly from the 16% of zero-day malware blocks reported in October and the 19% monthly average reported for the year.
The latest high-profile zero day threat to surface is the Internet Explorer browser exploit, which has just been patched by Microsoft after being in the wild for a week.
A zero-day attack sees hackers exploit a vulnerability before the software provider realises there is a problem and has time to fix it.
"Throughout November, attackers were more intent than ever on ensuring the malware they used would bypass traditional security measures," said Mary Landesman, senior security researcher at ScanSafe.
"Given the dynamic and costly nature of today's web threats, real-time scanning of web traffic before it reaches the enterprise is more essential than ever."