TA17-132A: Indicators Associated With WannaCry Ransomware

["US-CERT" <US-CERT () ncas us-cert gov>]

U.S. Department of Homeland Security US-CERT

National Cyber Awareness System:



TA17-132A: Indicators Associated With WannaCry Ransomware [ https://www.us-cert.gov/ncas/alerts/TA17-132A ] 05/12/2017 
09:36 PM EDT 
Original release date: May 12, 2017 | Last revised: May 16, 2017

Systems Affected

Microsoft Windows operating systems

Overview

According to numerous open-source reports, a widespread ransomware campaign is affecting various organizations with 
reports of tens 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 latest version of this ransomware variant, known as WannaCry, WCry, or Wanna Decryptor, was discovered the morning 
of May 12, 2017, by an independent security researcher and has spread rapidly over several hours, with initial reports 
beginning around 4:00 AM EDT, May 12, 2017. Open-source reporting indicates a requested ransom of .1781 bitcoins, 
roughly $300 U.S.

This Alert is the result of efforts between the Department of Homeland Security (DHS) National Cybersecurity and 
Communications Integration Center (NCCIC) and the Federal Bureau of Investigation (FBI) to highlight known cyber 
threats. DHS and the FBI continue to pursue related information of threats to federal, state, and local government 
systems and as such, further releases of technical information may be forthcoming.

Description

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 [ https://technet.microsoft.com/en-us/library/security/ms17-010.aspx ] vulnerability on March 14, 2017. 
Additionally, Microsoft released patches for Windows XP, Windows 8, and Windows Server 2003 [ 
http://www.catalog.update.microsoft.com/Search.aspx?q=KB4012598 ] operating systems on May 13, 2017.

According to open sources, one possible infection vectormay be throughphishing.

Technical Details

"Indicators of Compromise (IOC)"

IOCs are provided within the accompanying .xlsx [ https://www.us-cert.gov/sites/default/files/ALERT_TA17-132A.xlsx ] 
file of this report.

IOCs were developed based on analysis of the malware and can be found in STIX [ 
https://www.us-cert.gov/sites/default/files/publications/TA17-132A_stix.xml ] format.

"Analysis"

Three files were submitted to US-CERT for analysis. All files are confirmed as components of a ransomware campaign 
identified as "WannaCry", a.k.a "WannaCrypt" or ".wnCry". The first file is a dropper, 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. For a list of IOCs found during 
analysis, see the STIX [ https://www.us-cert.gov/sites/default/files/publications/TA17-132A_stix.xml ] file.

Displayed beloware YARA signatures that can be used to detect the ransomware:

"Yara Signatures"

rule Wanna_Cry_Ransomware_Generic {

 meta:

 description = "Detects WannaCry Ransomware on Disk and in Virtual Page"

 author = "US-CERT Code Analysis Team"

 reference = "not set"

 date = "2017/05/12"

 hash0 = "4DA1F312A214C07143ABEEAFB695D904"

 strings:

 $s0 = {410044004D0049004E0024}

 $s1 = "WannaDecryptor"

 $s2 = "WANNACRY"

 $s3 = "Microsoft Enhanced RSA and AES Cryptographic"

 $s4 = "PKS"

 $s5 = "StartTask"

 $s6 = "wcry@123"

 $s7 = {2F6600002F72}

 $s8 = "unzip 0.15 Copyrigh"

 $s9 = "Global\WINDOWS_TASKOSHT_MUTEX"

 $s10 = "Global\WINDOWS_TASKCST_MUTEX"

 $s11 = {7461736B736368652E657865000000005461736B5374617274000000742E776E7279000069636163}

 $s12 = {6C73202E202F6772616E742045766572796F6E653A46202F54202F43202F5100617474726962202B68}

$s13 = "WNcry@2ol7"

 $s14 = "wcry@123"

 $s15 = "Global\MsWinZonesCacheCounterMutexA"

 condition:

 $s0 and $s1 and $s2 and $s3 or $s4 and $s5 and $s6 and $s7 or $s8 and $s9 and $s10 or $s11 and $s12 or $s13 or $s14 or 
$s15

}

/*The following Yara ruleset is under the GNU-GPLv2 license (http://www.gnu.org/licenses/gpl-2.0.html) and open to any 
user or organization, as long as you use it under this license.*/

rule MS17_010_WanaCry_worm {

 meta:

 description = "Worm exploiting MS17-010 and dropping WannaCry Ransomware"

 author = "Felipe Molina (@felmoltor)"

 reference = "https://www.exploit-db.com/exploits/41987/";

date = "2017/05/12"

 strings:

 $ms17010_str1="PC NETWORK PROGRAM 1.0"

 $ms17010_str2="LANMAN1.0"

 $ms17010_str3="Windows for Workgroups 3.1a"

 $ms17010_str4="__TREEID__PLACEHOLDER__"

 $ms17010_str5="__USERID__PLACEHOLDER__"

 $wannacry_payload_substr1 = "h6agLCqPqVyXi2VSQ8O6Yb9ijBX54j"

 $wannacry_payload_substr2 = "h54WfF9cGigWFEx92bzmOd0UOaZlM"

 $wannacry_payload_substr3 = "tpGFEoLOU6+5I78Toh/nHs/RAP"

 condition:

 all of them

}

 

"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 propigate 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.

Impact

Ransomware not only targets home users; businesses can also become infected with ransomware, leading to negative 
consequences, including


  * temporary or permanent loss of sensitive or proprietary information, 
  * disruption to regular operations, 
  * financial losses incurred to restore systems and files, and 
  * potential harm to an organizations reputation. 

Paying the ransom does not guarantee the encrypted files will be released; it only guarantees that the malicious actors 
receive the victims money, and in some cases, their banking information. In addition, decrypting files does not mean 
the malware infection itself has been removed.

Solution

*_Recommended Steps for Prevention _*


  * Apply the Microsoft patch for the MS17-010 SMB vulnerability dated March 14, 2017. 
  * Enable strong spam filters to prevent phishing emails from reaching the end users and authenticate in-bound email 
using technologies like Sender Policy Framework (SPF), Domain Message Authentication Reporting and Conformance (DMARC), 
and DomainKeys Identified Mail (DKIM) to prevent email spoofing. 
  * Scan all incoming and outgoing emails to detect threats and filter executable files from reaching the end users. 
  * Ensure anti-virus and anti-malware solutions are set to automatically conduct regular scans. 
  * Manage the use of privileged accounts. Implement the principle of least privilege. No users should be assigned 
administrative access unless absolutely needed. Those with a need for administrator accounts should only use them when 
necessary. 
  * Configure access controls including file, directory, and network share permissions with least privilege in mind. If 
a user only needs to read specific files, they should not have write access to those files, directories, or shares. 
  * Disable macro scripts from Microsoft Office files transmitted via email. Consider using Office Viewer software to 
open Microsoft Office files transmitted via email instead of full Office suite applications. 
  * Develop, institute, and practice employee education programs for identifying scams, malicious links, and attempted 
social engineering. 
  * Run regular penetration tests against the network, no less than once a year. Ideally, run these as often as 
possible and practical. 
  * Test your backups to ensure they work correctly upon use. 

*_Recommendations for Network Protection_*

Apply the patch (MS17-010). If the patch cannot be applied, consider:


  * Disabling SMBv1 and 
  * blocking all versions of SMB at the network boundary by blocking TCP port 445 with related protocols on UDP ports 
137-138 and TCP port 139, for all boundary devices. 

"*Note:* disabling or blocking SMB may create problems by obstructing access to shared files, data, or devices. The 
benefits of mitigation should be weighed against potential disruptions to users."

Review US-CERTs Alert on The Increasing Threat to Network Infrastructure Devices and Recommended Mitigations [ 
https://www.us-cert.gov/ncas/alerts/TA16-250A ] and consider implementing the following best practices:


  * Segregate networks and functions. 
  * Limit unnecessary lateral communications. 
  * Harden network devices. 
  * Secure access to infrastructure devices. 
  * Perform out-of-band network management. 
  * Validate integrity of hardware and software. 

*_Recommended Steps for Remediation_*


  * Contact law enforcement. We strongly encourage you to contact a local FBI field office upon discovery to report an 
intrusion and request assistance. Maintain and provide relevant logs. 
  * Implement your security incident response and business continuity plan. Ideally, organizations should ensure they 
have appropriate backups so their response is simply to restore the data from a known clean backup. 

*_Defending Against Ransomware Generally_*

Precautionary measures to mitigate ransomware threats include:


  * Ensure anti-virus software is up-to-date. 
  * Implement a data back-up and recovery plan to maintain copies of sensitive or proprietary data in a separate and 
secure location. Backup copies of sensitive data should not be readily accessible from local networks. 
  * Scrutinize links contained in emails, and do not open attachments included in unsolicited emails. 
  * Only download softwareespecially free softwarefrom sites you know and trust. 
  * Enable automated patches for your operating system and Web browser. 

*_Report Notice_*

DHS and FBI encourages recipients who identify the use of tool(s) or techniques discussed in this document to report 
information to DHS or law enforcement immediately. We encourage you to contact DHSs National Cybersecurity and 
Communications Integration Center (NCCIC) (NCCICcustomerservice () hq dhs gov [ 
https://www.us-cert.govmailto:NCCICCustomerService () hq dhs gov ] or 888-282-0870), or the FBI through a local field 
office or the FBIs Cyber Division (CyWatch () ic fbi gov  [ https://www.us-cert.govmailto:CyWatch () ic fbi gov ]or 
855-292-3937) to report an intrusion and to request incident response resources or technical assistance.

References

  * Malwarebytes LABS: WanaCrypt0r ransomware hits it big just before the weekend [ 
https://blog.malwarebytes.com/cybercrime/2017/05/wanacrypt0r-ransomware-hits-it-big-just-before-the-weekend/ ] 
  * Malwarebytes LABS: The worm that spreads WanaCrypt0r [ 
https://blog.malwarebytes.com/threat-analysis/2017/05/the-worm-that-spreads-wanacrypt0r/ ] 
  * Microsoft: Microsoft Security Bulletin MS17-010 [ 
https://technet.microsoft.com/en-us/library/security/ms17-010.aspx ] 
  * Forbes: An NSA Cyber Weapon Might Be Behind A Massive Global Ransomware Outbreak [ 
https://www.forbes.com/sites/thomasbrewster/2017/05/12/nsa-exploit-used-by-wannacry-ransomware-in-global-explosion/#4fb6a207e599
 ] 
  * Reuters: Factbox: Don't click - What is the 'ransomware' WannaCry worm? [ 
http://www.reuters.com/article/us-britain-security-hospitals-ransomware-idUSKBN1882O2 ] 
  * GitHubGist: WannaCry|WannaDecrypt0r NSA-Cyberweapon-Powered Ransomware Worm [ 
https://gist.github.com/rain-1/989428fa5504f378b993ee6efbc0b168 ] 
  * Microsoft: Microsoft Update Catalog: Patches for Windows XP, Windows 8, and Windows Server 2003, (KB4012598) [ 
http://www.catalog.update.microsoft.com/Search.aspx?q=KB4012598 ] 
  * Cisco: Player 3 Has Entered the Game: Say Hello to 'WannaCry' [ 
http://blog.talosintelligence.com/2017/05/wannacry.html ] 
  * Washington Post: More than 150 countries affected by massive cyberattack, Europol says [ 
https://www.washingtonpost.com/business/economy/more-than-150-countries-affected-by-massive-cyberattack-europol-says/2017/05/14/5091465e-3899-11e7-9e48-c4f199710b69_story.html
 ] 

Revision History

  * May 12, 2017: Initial post 
  * May 14, 2017: Corrected Syntax in the second Yara Rule 
  * May 14, 2017: Added Microsoft link to patches for Windows XP, Windows 8, and Windows Server 2003 
  * May 14, 2017: Corrected Syntax in the first Yara Rule 
  * May 16, 2017: Provided further analysis and new IOCs in STIX format 
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