Websense estimates that close to 70 percent of Windows-based PCs are vulnerable to attack, by a zero-day exploit.
The vulnerability allows attackers to execute code on a machine when the user visits a malicious website.
This can happen when the user is tricked into clicking a link in an email or via compromised legitimate websites.
Websense senior security research manager Carl Leonard said the discovery suggests that the hackers were using this exploit to specifically target companies in APAC.
"Websense estimates that close to 70 percent of Windows-based PCs are vulnerable to this exploit," he said. "Given the huge attack surface, the actors behind these campaigns are racing to target companies before a patch becomes available.
"We anticipate that as more information of this zero day comes to light, the exploit will be weaponised and packaged into exploit kits rapidly, greatly increasing the number of attackers with access to this exploit.
But Leonard said all was not lost as they generally fell into an attack pattern.
"When you take the approach of looking at the entire attack chain for suspicious behaviour, rather than waiting and hoping to catch something on the last step of the process, you have many more opportunities to spot and disrupt an attack - even if it's malware you've never seen before," he said.
"Websense strongly encourages IT administrators to install the Microsoft FixIt patch to stop the vulnerability while waiting for a formal patch from Microsoft."
Sign up for CIO Asia eNewsletters.