US officials and Microsoft executives say older versions of the programs may be vulnerable to malware. In the advisory, NSA officials said a flaw known as "BlueKeep" exists in past editions of Microsoft Windows. Last week Microsoft warned that "some older versions of Windows" could be vulnerable to cyber-attacks. "All customers on affected operating systems [Windows 7 and earlier] should update as soon as possible," said Microsoft. US officials said the "BlueKeep" flaw could leave computers vulnerable to infection by viruses through automated attacks or by the downloading of malicious attachments. They said ransomware can often be installed quickly, holding files hostage and demanding payment from individuals. The vulnerability in the older versions of Microsoft Windows wrote the International Computer Science Institute's Nicholas Weaver, means that bad actors could "gain complete control of the remote system". Updating systems, as the Microsoft executives explained, helps to protect computer users from these kinds of cyber-attacks. Recently a ransomware attack on the city of Baltimore disrupted municipal services, knocking city workers offline and making it harder for people to pay their traffic tickets and water bills. The New York Times has reported that the NSA knew about the system flaw, EternalBlue, but kept it secret for years. EternalBlue has been implicated in a range of cyber-attacks over the past three years, including the WannaCry assault that disrupted the UK's NHS. A senior NSA adviser, Rob Joyce, tweeted on his own account that some computer users could face a "significant risk" because of the vulnerabilities in the older versions of Microsoft Windows, but that they would be protected by updates. Read more of this warning on OUR FORUM.