By now you should have seen the news of widespread ransomware attacks. It is projected to have affected users in more than 150 countries.
In this attack ransomware called WannaCry was emailed to users. When opened, the malware locked files on their computers. Older versions of Microsoft Windows systems that have not applied security patches were affected.
The patches to defend against this type of attacks have been available for a while. See: https://isc.sans.edu/forums/diary/Massive+wave+of+ransomware+ongoing/22412/(link is external)
If you have not already applied this patch, please do so immediately. If you suspect infection from this attack, contact email@example.com immediately.