The launch of Windows 10 is used by cybercriminals to distribute malware by email, according to Cisco. They send out mails that appear to be coming from update@microsoft.com with a file attached that should trick users thinking they can upgrade by running that file.
Windows 7 and 8.1 users can upgrade for free to Windows 10 the coming year. Microsoft has started to distribute the update since July 29th and cybercriminals are using the event to try to infect internet users with ransomware.
Emails that appear to be coming from Microsoft state the user can upgrade to Windows 10 for free and that they can run the attached installer to start the process. In reality the attachment with the name "Win10installer.zip" is a ransomware variant that encrypts files and demands ransom.
Infected users have 96 hours to pay the ransom in Bitcoin or else they lose their files. Cisco reports that the ransomware is currently distributed on large scale.
