Windows Defender AV detects and removes this threat.

This ransomware can stop you from using your PC or accessing your data. Unlike other ransomware, however, this threat has worm capabilities. It uses an exploit code for a patched SMB vulnerability, CVE-2017-0145. This vulnerability was fixed in security bulletin MS17-010, which was released on March 14, 2017. We remind all customers to keep computers up-to-date.

The exploit code used by this threat to spread to other computers was designed to work only against unpatched Windows 7 and Windows Server 2008 (or earlier OS) systems. The exploit does not affect Windows 10 PCs.

For more information about this ransomware (which is also known as WannaCrypt, WannaCry, WanaCrypt0r, WCrypt, or WCRY), you can read the following entries on the Windows Security blog and Microsoft Security Response Center:

• WannaCrypt ransomware worm targets out-of-date systems
• Customer Guidance for WannaCrypt attacks

Our ransomware FAQ page has more information on this type of threat.

The trend towards increasingly sophisticated malware behavior, highlighted by the use of exploits and other attack vectors, makes older platforms so much more susceptible to ransomware attacks. From June to November 2017, Windows 7 devices were 3.4 times more likely to encounter ransomware compared to Windows 10 devices.

Read our latest report: A worthy upgrade: Next-gen security on Windows 10 proves resilient against ransomware outbreaks in 2017.