Preventing Petya and Other Types of Ransomware

The recent ransomware events have a few things in common – they target Windows operating systems and are largely preventable, but IT organizations have to remain diligent with applying patches.

For example, in March of this year, Microsoft patched a flaw in SMBv1, a legacy file-sharing protocol in Windows. Despite the availability of the update, two months later, the WannaCry virus affected tens of thousands of Windows devices around the globe. WannaCry exploited the SMB vulnerability previously patched by Microsoft, making it entirely preventable. And such was the magnitude of the event that Microsoft went out of its way to patch the now unsupported Windows XP and Windows 2003 Server, even though WannaCry didn’t target these operating systems.

Another global incident occurred at the end of June. Petya was an evolution of WannaCry—also exploiting the same SMBv1 vulnerability but adding worm capabilities to spread throughout a network. Although unlike WannaCry, it’s believed that Petya was designed to wipe out data and cause chaos, rather than hold the data ransom.

According to Kaspersky Labs, 95% percent of all devices infected by WannaCry were running Windows 7. Windows 10 devices were largely unaffected because of built-in mitigation technologies but could be vulnerable to new variants in the future. Additionally, a study by RiskSense showed that Windows 10 Threshold 2 (version 1511) is the last version of the OS vulnerable to the SMBv1 exploit, demonstrating the importance of updating.

If you want to apply Microsoft’s recommended security settings, the Group Policy Object (GPO) backups in the Security Compliance Toolkit can be used to quickly configure Window 10 and Windows Server 2016. The security baseline guide for Windows 10 version 1709 includes Group Policy templates that allow organizations to disable SMBv1. And if your organization doesn’t need SMBv1, Microsoft recommends you disable it.

The Windows 10 Fall Creators Update (version 1709) won’t include server component of SMBv1 if you perform a clean install. In an upgrade scenario, the SMBv1 server component will remain if it was previously available. And it’s worth noting that the Windows 10 Creators Update (version 1703) includes the SMB 1.0/CIFS File Sharing Support feature. Home and Pro editions will still include the SMBv1 client, but SMBv1 is being completely removed from Enterprise and Education.

But SMBv1 isn’t the only potentially vulnerable component in Windows. Petya uses a payload like the Mimikatz framework to steal credentials using PowerShell, enabling it to move laterally across the network. That’s not to say that PowerShell is dangerous and should be disabled. On the contrary, it is the most secure way to manage Windows.

Implementing Microsoft’s best practice advice can reduce the risk of hackers exploiting management tools. Join me for my on-demand webinar, Preventing Petya and Other Types of Ransomware, where I discuss the mitigations I mentioned above in more detail, and:

• Removing administrative privileges to prevent ransomware attacks
• Staying up-to-date with patching
• Blocking SMB v1
• Deploying Application Control
• Managing macro security in Microsoft Office