More good information and I suggest reading through it all if you have not done so already. This is a bad weekend for business and infrastructure that is using older systems, but its been a good weekend for the infosec community in coming together and helping and sharing alot of good information with each other.
There is a tool you can run on a host that will stop the ransomware from encrypting your machine, however it will still attempt to spread over your network.
This is a pretty good write up of what was known at the time.
There have been easy fixes for this available for the past 2 months and it was just a matter of time until the tools that were developed by our American Friends, that they would be used against the general public.
Hopefully this is lessons learned for many organisations, and they realise that patching and running fairly up to date operating systems is important and not just something to achieve compliance.
Few more articles that contain good information about these events.
Vector: All Windows versions before Windows 10 are vulnerable if not patched for MS-17-010. It uses EternalBlue MS17-010 to propagate.
Ransom: between $300 to $600. There is code to ‘rm’ (delete) files in the virus. Seems to reset if the virus crashes.
Backdooring: The worm loops through every RDP session on a system to run the ransomware as that user. It also installs the DOUBLEPULSAR backdoor. It corrupts shadow volumes to make recovery harder. (source: malwarebytes)
Kill switch: If the website www.iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea.com is up the virus exits instead of infecting the host. (source: malwarebytes). This domain has been sinkholed, stopping the spread of the worm. Will not work if proxied (source).
update: A minor variant of the virus has been found, it looks to have had the killswitch hexedited out. Not done by recompile so probably not done by the original malware author. On the other hand that is the only change: the encryption keys are the same, the bitcoin addresses are the same. On the other hand it is corrupt so the ransomware aspect of it doesn’t work – it only propagates.
To be infected requires the SMB port (445) to be open, or the machine already infected with DOUBLEPULSAR (and killswitch not registered or somehow blocked, or the network accessing it through a proxy).
The MS17-010 patch fixes the vulnerability.
Windows XP: Doesn’t spread. If run manually, can encrypt files.
Windows 7,8,2008: can spread unpatched, can encrypt files.
There are a number of files and folders wannacrypt will avoid. Some because it’s entirely pointless and others because it might destabilize the system. During scans, it will search the path for the following strings and skip over if present:
“Content.IE5”
“Temporary Internet Files”
” This folder protects against ransomware. Modifying it will reduce protection”
typedef struct _wc_file_t {
char sig[WC_SIG_LEN] // 64 bit signature WANACRY!
uint32_t keylen; // length of encrypted key
uint8_t key[WC_ENCKEY_LEN]; // AES key encrypted with RSA
uint32_t unknown; // usually 3 or 4, unknown
uint64_t datalen; // length of file before encryption, obtained from GetFileSizeEx
uint8_t *data; // Ciphertext Encrypted data using AES-128 in CBC mode
} wc_file_t;
credit for reversing this file format info: cyg_x11.
Vulnerability disclosure
The specific vulnerability that it uses to propagate is ETERNALBLUE.
This was developed by “equation group” an exploit developer group associated with the NSA and leaked to the public by “the shadow brokers”. Microsoft fixed this vulnerability March 14, 2017. They were not 0 days at the time of release.
