The last few days of the cybersecurity community have been heated up by a vast-scale ransomware attack rippling across the world. On Friday 12 May came the first announcements of victims infected with a ransomware dubbed WannaCry (also known as WCry or Wanna Decryptor). It soon became clear that the scale of this wave was bigger than usual. According to the last estimates, the malware infected more than 250,000 systems in as many as one hundred countries. The list of victims is long and includes notorious names across all sectors. In some cases, the malware had unfortunate consequences. For instance, a few hospitals in the United Kingdom had to cancel their scheduled surgeries and some students in China lost their graduation thesis.
What we know
The malware encrypts and adds the extension “.WCRY” to all files that match a list of 176 specific extensions including documents, database and backup files. The victim is requested to pay between USD 300 and 600 in Bitcoins to get its files back. So far, there is no evidence that a payment will effectively provide the key for decrypting the files. In their message, the authors threaten to delete the file forever if their request is not met within eight days. The international ambitions of this campaign are made clear by the fact that the ransom message is translated in 28 languages.
Once the initial host has been infected, the ransomware dropper makes use of the MS17-010 vulnerability of the Server Message Block (SMB) protocol to spread laterally through the network. The exploit using this vulnerability has been made public by the group Shadow Broker on 14 April 2017 in a leak of hacking tools allegedly crafted by a state actor. Microsoft had released a patch a month before.
Switzerland has not been spared. The Swiss GovCERT declared that until Sunday evening there were roughly 200 potential victims. The number of victims could steeply increase, as there are more than 5,000 systems directly connected to the Internet over a SMB protocol.
What is still unclear
Despite the overwhelming information, some points still remain unclear. First, it is not yet known how the dropper is initially delivered to the victims. According to one hypothesis a spear phishing e-mail should have spread the malicious attachment. However, no such e-mails have surfaced yet. In its alert, the US-CERT claimed that hackers gained access to the victims’ network either through Remote Desktop Protocol or through the exploitation of the critical Windows SMB vulnerability mentioned above. Second, the identity of the authors is wrapped in mystery. Given the financial nature of the attack, the dominant hypothesis states that the attack has been launched by a criminal group. However, it should not be forgotten that in the past even state actors were involved in spectacular heists. Fresh discoveries suggest that the malware might be linked to Lazarus, a state actor group believed to be involved in the infamous SWIFT attack against the Bangladesh Central Bank of February 2016. So far, the authors have neither spent nor transferred the Bitcoins they obtained. At this stage, it is difficult to make further assertions on the attribution of the attack.
As previously mentioned, the exploit used in this attack was leaked in April this year. By that time, the vendor had already released a patch to correct the flaws. Unfortunately, many users ignored this threat and were not much eager to install the patch. This episode should serve as a reminder that threat actors will reuse leaked tools and that without a proper prophylaxis an incident is just around the corner.
As reported by the media, a young IT-security researcher could temporarily curb the attack by registering a “kill-switch” domain that told the ransomware to stop spreading itself. Unfortunately, new versions of the malware without this feature have already been spotted in the wild. Furthermore, the threat intelligence community generously shared a lot of indicators and advices helping organisations to identify, prevent and dwarf the impact of infections. These common efforts have to be praised and should continue in the future.
If not done yet, apply the MS17-010 patches immediately. As short-term actions, your IT team should consider to:
- disable all external SMB access (blocking ports 137, 139 and 445 to/from the internet);
- disable the use of the SMBv1 network file sharing protocol;
- ensure two-factor authentication is in place for all necessary external accesses to systems (e.g. VPN and RDP);
- update the antivirus signatures;
- rapidly isolate the infected system from your corporate network to curb the spreading of the infection;
- backup the encrypted files in case a decryption tool become available, if you have already fallen victim to the ransomware.
On a more long-term approach, consider to plan and exercise a business continuity programme, adopt and test an incident response strategy, a consistent patch and vulnerability management, as well as a regular backup policy and security awareness raising trainings.
PwC can provide you with the necessary assistance and counsel to address these issues and improve your overall security posture. PwC strongly believes in a holistic approach to cyber security by offering a wide variety of services covering all the phases of the cyber lifecycle: from strategy and policy development to its implementation and review.
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