We are aware of a widespread ransomware attack which is affecting several IT organizations in multiple countries. A new ransomware attack called Wanna (also known as WannaCry, WCry, WanaCrypt, WanaCrypt0r and Wana DeCrypt0r) is encrypting files and changing the extensions to: .wnry, .wcry, .wncry and .wncrypt. The malware then presents a window to the user with a ransom demand.
The ransomware spreads rapidly, like a worm, by exploiting a Windows vulnerability in the Windows Server Message Block (SMB) service, which Windows computers use to share files and printers across local networks. Microsoft addressed the issue in its MS17-010 bulletin.
Analysis seems to confirm that the attack was launched using suspected NSA code leaked by a group of hackers known as the Shadow Brokers. It uses a variant of the ShadowBrokers APT EternalBlue Exploit (CC-1353). It uses strong encryption on files such as documents, images, and videos.
Sophos Customers using Intercept X and Sophos EXP products will also see this ransomware blocked by CryptoGuard. Please note that while Intercept X and EXP will block the underlying behavior and restore deleted or encrypted files in all cases we have seen, the offending ransomware splashscreen and note may still appear.
Sophos has issued protection for this threat:
For information on IPS protection in the Sophos XG Firewall, Sophos UTM or Cyberoam Firewall please see this article: IPS protection against the EternalBlue vulnerability CVE-2017-0144
Please ensure all of your Windows environments have been updated as described in Microsoft Security Bulletin MS17-010 - Critical. Microsoft is providing Customer Guidance for WannaCrypt attacks
Microsoft has made the decision to make the Security Update for platforms in custom support only, Windows XP, Windows 8, and Windows Server 2003, broadly available for download:
Applying the Microsoft patches MS17-010 should be enough to protect against the EternalBlue Exploit that enabled the rapid spread of the Wanna ransomware attack. Microsoft and others are advising that customers should consider blocking legacy protocols on their networks in particular SMBv1 as an additional defense-in-depth strategy to further protect against attacks.
Customers considering disabling SMBv1 should proceed with caution since this could cause software and other services that depend on SMB to stop functioning correctly. In particular, please see the following article for information regarding disabling SMBv1 for Sophos products: What to do if you decide to disable SMBv1 as a response to Wanna ransomware
The Wanna malware variants that we have seen include a lookup to a URL. If the malware gets a response, the attack stops. This has been described in some media reports as a “kill switch”. The domain for the URL was registered and activated by an independent malware analyst intending to track the malware, meaning that if current variants of the ransomware can reach the URL the attack would stop.
As a result, the National Cyber Security Centre (NCSC) provide this advice: Finding the kill switch to stop the spread of ransomware. NCSC recommends the following domains to be in the Allow List in your environment:
(remove square brackets  when Allow Listing). Sophos has categorized these domains as Other/Computers & Internet.
To ensure that no other compromised code associated with this attack is still running in memory we advise customers reboot their computers after following the actions below.
We will continue to update this article as further information becomes available.
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