The WannaCry ransomware attacks that crippled hospitals in the United Kingdom on Friday have temporarily halted, although not before infections spread to 150 countries around the globe. The massive ransomware campaign saw 61 NHS Trusts in the UK affected.
As the NHS was cancelling appointments and scrambling to halt the spread of the infection and restore its systems, the WannaCry ransomware attacks were going global. Organizations around the world were waking up to total chaos, with systems taken out of action and data access blocked. Other victims include FedEx, Telefonica, Deutsche Bahn and the Russian Interior Ministry and around 200,000 others.
The victim count rose considerably throughout Friday and Saturday morning, before a security researcher in the UK accidentally flicked the ransomware’s kill switch, preventing further WannaCry ransomware attacks. Had it not been for that researcher’s actions, the victim count would have been considerably higher.
The researcher in question prefers to remain anonymous, although he tweets under the Twitter account @MalwareTechBlog. While analyzing the ransomware, he discovered a reference to a nonsense web domain. He checked to see who owned the domain and discovered it had not been registered. He bought it and realized that his actions had stopped the ransomware in its tracks. If the domain could be contacted, encryption would not take place. If contact was not possible, the ransomware would proceed and encrypt files on the infected device.
This kill switch could have been put in place by the authors as a way to stop infections getting out of control. However, far more likely is the domain check was performed to determine if the ransomware was running in a test environment.
For now at least, the WannaCry ransomware attacks have stopped, although that does not mean they will not continue. New versions of the ransomware – without the kill switch – will almost certainly be released. In the meantime, IT security professionals have some time to plug the vulnerability that was exploited.
The exploit takes advantage of a vulnerability in Windows Server Message Block (SMB) that allows the attackers to download files onto a vulnerable machine. Microsoft issued a patch to plug the vulnerability on March 13 (MS17-010). Even though this was a high priority patch for which an exploit had been developed (ETERNALBLUE) and released online, many companies failed to update Windows leaving them vulnerable to attack.
Of course, any organization using an unsupported version of Windows – Windows XP for example – would not be able to apply the patch. Many NHS Trusts in the UK still use the unsupported version of Windows even though it is vulnerable to this and other exploits.
The attackers have reportedly made around $50,000 so far from the WannaCry ransomware attacks. That figure will rise, as victims are given 7 days to pay before the decryption keys held by the attackers will be permanently deleted. If payment is not made within 3 days, the $300 ransom doubles.
There are no clues as to who was behind the attack, although it was made possible by the actions of the hacking group Shadow Brokers, who published the exploit used in the WannaCry ransomware attacks in April. The exploit was not developed by Shadow Brokers however. That appears to have been developed by the National Security Agency in the USA. Shadow Brokers allegedly stole the exploit.
Microsoft has responded to the WannaCry ransomware attacks saying they should serve as a “wake-up call.” That’s not just the need to apply patches promptly to prevent cyberattacks, but also a wake up call for governments not to secretly stockpile exploits.