WannaCry Ransomware Explained

Yes, the title is a play on words, but it’s dead on for the recent worldwide ransomware outbreak of WannaCry. So why do “I want to cry”? Because of the sloppy press, news, and poor facts surrounding this pandemic. I have seen local news reports stating, “Do not click on email links that could launch WannaCry,” and, “WannaCry was developed by the NSA.” Both make me shiver as a security professional, because neither is accurate.

Once More, From the Top

WannaCry is a ransomware payload that was grafted onto a vulnerability discovered by the NSA and leaked by Shadow Brokers. It was patched by Microsoft in March under advisory MS17-010. The hackers leveraged the vulnerabilities (nicknamed EternalBlue and DoublePulsar), refined an exploit, and grafted WannaCry (real name WanaCrypt0r) as the payload.

How WannaCry Propagated

The exploitation and delivery of WannaCry do not need any user interaction to infect a host. The payload contains its own network scanner that can find additional hosts and self-propagate the infestation to compromise as many systems as possible. This is how it spread so fast and through so many companies without anyone clicking on a link or browsing a malicious website.

Not since 2008 has a vulnerability been so bad and contained a privileged escalation threat of this nature that could be worm-able throughout Microsoft operating systems. Ten years later, penetration testing teams still find the flaw in the form of Conficker. As for WannaCry, early reports did indicate that an email was involved in early threats. Unfortunately, this information was deemed from the generic nature of ransomware and not WannaCry itself.

How Ransomware Works

Ransomware can compromise an asset via two primary vectors: privileges and vulnerabilities. When a privileged attack occurs, typically through social engineering tactics like phishing, a user is tricked into executing malware that begins the ransomware campaign. Depending on the ransomware type, the user’s privileges may stop the execution dead in its tracks, limit the exposure to the standard user’s files, or if they are an administrator potentially infect the entire environment. This is how privileged access management, and reducing user’s privileges can stop most ransomware; but not WannaCry.

The second form of ransomware is just a payload to a vulnerability and its corresponding exploit. This is the case with WannaCry. EternalBlue is a critical vulnerability that is wormable and can attack any susceptible Windows host and launch the ransomware. There is nothing an organization can do. Any Windows host that has the following characteristics can be exploited:

  • Does not have the March MS17-010 patch applied
  • Has SMB v1 enabled
  • Has the Server Service running
  • Has NetBIOS ports open and/or not filtered (specifically 445)

How to Remediate

WannaCry was just the result of exploitation but the payload could have been anything – from erasing the hard drive to a denial of service attack by creating a botnet.

Take these steps immediately to assess and address your risk:

  • Using Retina or another scanner, identify vulnerable hosts and patch with MS17-10. Retina can find these hosts and even patch for end-of-life operating systems, like Windows XP or Server 2003, with its integrated patch management capabilities.
  • Disable or Block SMBv1 – this is a temporary measure to stop the propagation, but does not remediate the threat.
  • If systems are public, or you suspect an outbreak before you have patched, turn the computers off.

Microsoft released an out-of-band patch for End-of-Life Windows operating systems including XP, Vista, Server 2003 and 2008, to protect against the WannaCry threat.

To identify at-risk systems, scan using these audits with your current Retina solution, or with Retina Community:

  • Vista / 2008: 62804 – Microsoft Security Update for Windows SMB Server (4013389) – 4012598
  • Windows 7: 62790 – Microsoft Security Update for Windows – March 2017 (4012212/4012215) – Windows 7
  • Windows 8.1: 62797 – Microsoft Security Update for Windows – March 2017 (4012213/4012216) – Windows 8.1
  • Window Server 2008 R2: 62791 – Microsoft Security Update for Windows -March 2017 (4012212/4012215) – 2008R2
  • Windows Server 2012: 62801 – Microsoft Security Update for Windows – March 2017 (4012214/4012217) – 2012Windows Server 2012R2: 62798 – Microsoft Security Update for Windows -March 2017 (4012213/4012216) – 2012R2

BeyondTrust is unique in that we can help organizations stay protected against vulnerability-related ransomware, such as WannaCry, with our Retina CS vulnerability management solutions, as well against privilege-related ransomware with our PowerBroker privileged access management solutions. For more information on how integrating these solutions can mitigate the risks of ransomware, contact us today.