WannaCry FAQ

What Happened?

  • On Friday May 12th 2017, several organisations were affected by a new Ransomware strain.
  • The Ransomware was very successful in part because it used a SMB vulnerability to spread inside networks.
  • The vulnerability was patched by Microsoft in March for supported versions of Windows.
  • The exploit, known under the name ETERNALBLUE, was released in April as part of a leak of NSA tools.
  • Variants have been seen spreading Saturday/Sunday.

How many infections?

  • Several large organisations world wide are known to be affected.
  • No obvious targeting. The organisations are from various countries and appear not to be related.
  • While large enterprises made the news, small business users and home users may be affected as well.
  • Estimated > 200,000 victims according to various anti virus vendors

How do systems get infected?

  • E-Mail: Some organisations suggest that the initial infection originated from e-mail attachments, but little is known about the e-mails. It is easily possible that other malware was confused with WannaCry.
  • SMB: Affected organisations may have had vulnerable systems exposed via port 445.
  • Up to now, affected organisations have not shared a lot of proof to show how the initial infection happened.

What happens to the victim?

  • Files with specific extensions will be encrypted.
  • The victim will see a ransom message asking for approx. $300. Ransomware demands will increase to $600 after 3 days. After 7 days, the files may not longer be recoverable.
  • The ransomware will also install a backdoor to access the system remotely via port 445 (Double Pulsar, also part of the NSA tool set).

How to Prevent Infection: Patch

  • Newer Windows Versions (Windows Vista, 7-10, Windows Server 2008-2016) can be patched with MS17-010 released by Microsoft in March.
  • Microsoft released a patch for older systems going back to Windows XP and Windows 2003 on Friday.
  • Confirm that patch is installed

Other Mitigating Controls

  • Segment Network
  • Prevent internal spreading via port 445 and RDP.
  • Block Port 445 at perimeter.
  • Disable SMBv1
  • Implement internal “kill switch” domains / do not block them
  • Set registry key.
  • At least one additional variant of the malware was seen this weekend. It uses a different “kill switch”.

Detect Affected Systems

  • Systems that are infected by WannaCry will try to connect to a specific domain.
  • Encrypted files will have the “wncry” extension.
  • Systems will scan internally for port 445.
  • Ransom message will be displayed.
  • In addition, infected systems will reach out to sites for crypto keys.
  • Anti-Malware has signatures now for WannaCry.

Ransom Note

Cleaning Up Infected Systems

  • Anti-Malware vendors are offering removal tools – ok for personal use.
  • Removal tools with remove malware, but will not recover encrypted files. Make a copy in case a decryptor becomes available.
  • WannaCry will install a backdoor that could be used to compromise the system further – for UO owned devices, wipe and reinstall.
  • Note that not all files with the .wncry extension are encrypted. Some may still be readable.

Kill Switch

  • The malware will not run if it can access a specific website.
  • This web site has been registered to stop the spread of malware.
  • But proxies may prevent connections. An internal website may be more reliable and allows detecting infections.
  • A registry entry was found that will prevent infection as well, and a tool was released to set the entry.
  • Future versions will likely remove these kill switches or change the name of the registry entry.

Will Paying the Ransom Help Us?

  • There is no public report from victims who paid the ransom.
  • About a hundred victims paid so far.
  • The unlock code is transmitted in a manual process that requires the victim to contact the person behind the ransomware to transmit an unlock code.
  • Due to the law enforcement and public attention, it is possible that the individual(s) behind this malware will disappear and not release unlock codes in the future.



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