Guy Ngongang

The world has experienced a Cyber Attack according to numerous open-source, classified as a ransomware campaign.It created ten of thousands of infections in Over 150 countries including the United States, United Kingdom,Spain, Russia, Taiwan,France and Japan. The software can run in as many as 27 different languages.The piece of code is affecting only Microsoft Windows Operating system. The latest version of this malware (5bef35496fcbdbe841c82f4d1ab8b7c2) was discovered in the morning of May 12 ,2017 by an independent security researcher. It was named Wannacry because of the string “WNcry@2ol7” found in its code.Open-source reporting indicates a requested ransom of .1781 bitcoins, roughly $300 U.S.

TECHNICAL DETAILS

Initial reports indicate the hacker or hacking group behind the WannaCry campaign is gaining access to enterprise servers through the exploitation of a critical Windows SMB vulnerability. Microsoft released a security update for the MS17-010 vulnerability on March 14, 2017. Additionally, Microsoft released patches for Windows XP, Windows 8, and Windows Server 2003 operating systems on May 13, 2017. According to open sources, one possible infection vector may be through phishing. There exists 3 files belonging to the same malware.The first file is a dropper(worm), which contains and runs the ransomware, propagating via the MS17-010/EternalBlue SMBv1.0 exploit. The remaining two files are ransomware components containing encrypted plug-ins responsible for encrypting the victim users files.

 

Dropper

This artifact (5bef35496fcbdbe841c82f4d1ab8b7c2) is a malicious PE32 executable that has been identified as a WannaCry ransomware dropper. Upon execution, the dropper attempts to connect to the following hard-coded URI:

http[:]//www[.]iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea.com.

Displayed below is a sample request observed:

--Begin request—

GET / HTTP/1.1
Host: www[.]iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea.com
Cache-Control: no-cache

--End request--

If a connection is established, the dropper will terminate execution. If the connection fails, the dropper will infect the system with ransomware.
When executed, the malware is designed to run as a service with the parameters “-m security”. During runtime, the malware determines the
number of arguments passed during execution. If the arguments passed are less than two, the dropper proceeds to install itself as the
following service:

--Begin service--

ServiceName = "mssecsvc2.0"
DisplayName = "Microsoft Security Center (2.0) Service"
StartType = SERVICE_AUTO_START
BinaryPathName = "%current directory%5bef35496fcbdbe841c82f4d1ab8b7c2.exe -m security"

--End service--

Once the malware starts as a service named mssecsvc2.0, the dropper attempts to create and scan a list of IP ranges on the local network
and attempts to connect using UDP ports 137, 138 and TCP ports 139, 445. If a connection to port 445 is successful, it creates an additional
thread to propigate by exploiting the SMBv1 vulnerability documented by Microsoft Security bulliten MS17-010. The malware then extracts &
installs a PE32 binary from it’s resource section named “R”. This binary has been identified as the ransomware component of WannaCrypt.
The dropper installs this binary into “C:\WINDOWS\tasksche.exe.” The dropper executes tasksche.exe with the following command:

--Begin command--

"C:\WINDOWS\tasksche.exe /i"

--End command—

 

NOTE:When this sample was initially discovered, the domain “iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea[.]com” was not registered, allowing the
malware to run and propagate freely. However within a few days, researchers learned that by registering the domain and allowing the
malware to connect, it’s ability to spread was greatly reduced. At this time, all traffic to “iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea.com” is
re-directed to a monitored, non-malicious server, causing the malware to terminate if it is allowed to connect. For this reason, we recommend
that administrators and network security personnel not block traffic to this domain.

RANSOMWARE COMPONENTS

The malware creates a 2048 bit RSA key pair. The private key is encrypted using a public key that is included with the malware. For each file, a new random AES key is generated. This random AES key is then encrypted using the public user key. To decrypt the files, the user’s private key needs to be decrypted, which requires the malware author’s private key. Unlike some other ransomware, no network communication is needed to generate these keys [pastebin]. The password “WNcry@2ol7” is not used to encrypt files. It is only used by the malware to decrypt some of its components. Encrypted files use the extension. wncry. To decrypt the files, the user is asked to pay $300, which will increase to $600 after a few days. The ransomware threatens to delete all files after a week.

SOLUTION

-Apply the MS patch

-Basic defense in depth meaning segmentation to isolate vulnerable machines

-Restrict TCP port 445

-use Private Vlans if your edge switches support this feature

-Ensure anti-virus and anti-malware solutions are set to automatically conduct regular scans.

-Test your backups to ensure they work correctly upon use

-Implement the principle of least privilege

References: IOC with Wannacry:US-CERT

Washington post 150 countries affected