CERT NZ has advised that Microsoft has released information about an issue in older Windows operating systems which allows attackers to remotely connect to systems and gain control of that system.
CERT NZ, which is the government cyber security agency, says Microsoft has released software updates for all affected versions.
"CERT NZ recommends you update your operating system as soon as possible. Once you have updated your software you are no longer at risk," it says.
The systems at risk are Windows 7 and Windows XP. Windows 8 and Windows 10 are not affected.
CERT NZ says businesses should note that some versions of Windows Server are at risk as well. These are Windows Server 2008 R2, 2008 and 2003.