On May 12th 2017 a ransomware variant known as WanaCry has been spread on a massive scale around the world. The initial infection vector appeared to be phishing e-mails.
Once a computer is infected it will attempt to infect other machines on the same network using a recently patched Windows vulnerability.
Update: We have published an FAQ to answer additional questions about the ransomware outbreak
- Apply Windows update MS17-010
- Microsoft has also released a patch for Windows XP.
- Disable the outdated protocol SMBv1
- Do not allow connections to the RDP or SMB protocol directly from the internet
- Isolate unpatched or unsupported systems from the internal network
- Make back-ups and verify that they can be restored
About this campaign
This ransomware campaign is especially dangerous as it spreads itself through the internal network using a recently patched Windows vulnerability.
Once a machine is infected it will scan the entire internal network and infect vulnerable machines.
Machines are not required to be connected to the internet for the encryption process to take place.
The exploit used by this ransomware campaign was leaked by a group known as the ‘Shadow Brokers’ and has now been repurposed by the attackers behind this campaign to infect machines in internal networks. Microsoft has released a patch for this specific vulnerability (MS17-010) on March 14th 2017. Machines that have been patched are not vulnerable to the exploit, but could still be infected through other infection methods such as phishing e-mails.
After looking at the ransomware’s code Fox-IT noticed that the malware had a hardcoded kill switch which could disable all functionality.
Once the ransomware is running on a victim’s machine it tries to connect to the domain iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea[.]com.
If the connection succeeds, the binary exits and will not start encrypting files nor start spreading.
It appears that a fellow security researcher (@MalwareTechBlog) spotted the domain and found out it was not registered by the attackers.
This was a sloppy mistake by the hackers, given the large campaign it was engaged in.
This security researcher has registered the domain name and as soon it was replying to requests it seems that the kill switch in the malware became active. This means that anyone who has received the actual phishing email but did not open it yet appears to have been saved.
The domain seems to be registered at 17:08:04 CEST. This could be one of the possible explanations as to why the hardcoded Bitcoin wallets have not received a large amount of Bitcoins.
The large amount of damage caused today and all international press attention have given everybody a heads up of what to expect.
With the majority of the big organizations starting with their weekend, offices are closed. System administrators and security personal could use this weekend to take prevention, detection and response measures. If everyone comes back in the office by Monday and a new wave of phishing attacks would start, without a kill-switch, the damage could be far less than expected at this stage. Though we have learned a lot, the cyber criminals will have as well.
Snort signatures from Emerging Threats are available for the ETERNALBLUE exploit:
The ransomware itself communicates using the Tor protocol.
One of the confirmed infection vectors is the usage of the ETERNALBLUE exploit directly on machines which have SMB directly exposed to the internet.
This chapter previously stated that we were in the process of verifying if phishing e-mails were also an infection vector for the WanaCry ransomware. Thus far Fox-IT has found no evidence that any phishing e-mails were related to this specific ransomware outbreak, and we have therefor removed the related indicators from this blog.
Command and Control servers
Available languages in the ransomware
- m_chinese (simplified)
- m_chinese (traditional)