Microsoft Windows operating systems
On June 27, 2017, NCCIC was notified of Petya ransomware events occurring in multiple countries and affecting multiple sectors. Petya ransomware encrypts the master boot records of infected Windows computers, making affected machines unusable.
The NCCIC Code Analysis Team produced a Malware Initial Findings Report (MIFR) to provide in-depth technical analysis of the malware. In coordination with public and private sector partners, NCCIC is also providing additional IOCs in comma-separated-value form for information sharing purposes.
The scope of this Alert’s analysis is limited to the newest “Petya” variant that surfaced June 27, 2017, and this malware is referred to as “Petya” throughout this Alert.
Based on initial reporting, this Petya campaign involves multiple methods of initial infection and propagation, including exploiting vulnerabilities in Server Message Block (SMB). Microsoft released a security update for the MS17-010 vulnerability on March 14, 2017. Background information on ransomware infections is provided in US-CERT Alert TA16-091A.
US-CERT received a sample of this Petya ransomware variant and performed a detailed malware analysis. The team found that this Petya variant encrypts the victim’s files with a dynamically generated, 128-bit key and creates a unique ID of the victim. However, there is no evidence of a relationship between the encryption key and the victim’s ID, which means it may not be possible for the attacker to decrypt the victim’s files even if the ransom is paid.
This Petya variant spreads using the SMB exploit as described in MS17-010 and by stealing the user’s Windows credentials. This variant of Petya is notable for installing a modified version of the Mimikatz tool, which can be used to obtain the user’s credentials. The stolen credentials can be used to access other systems on the network. This Petya variant will also attempt to identify other hosts on the network by checking the compromised system’s IP physical address mapping table. Next, it scans for other systems that are vulnerable to the SMB exploit and installs the malicious payload.
The compromised system’s files are encrypted with a 128-bit Advanced Encryption Standard (AES) algorithm during runtime. This Petya variant writes a text file on the “C:\” drive with the Bitcoin wallet information and RSA keys for the ransom payment. It modifies the master boot record (MBR) to enable encryption of the master file table (MFT) and the original MBR, then reboots the system. Based on the encryption methods used, it appears unlikely that the files can be restored even if the attacker received the victim’s unique ID.
According to multiple reports, this Petya ransomware campaign has infected organizations in several sectors including finance, transportation, energy, commercial facilities, and healthcare. While these victims are business entities, other Windows systems without patches installed for the vulnerabilities in MS17‑010, CVE-2017-0144, and CVE-2017-0145 are at risk of infection.
Negative consequences of ransomware infection include the following:
- 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 organization’s reputation.
NCCIC recommends against paying ransoms; doing so enriches malicious actors while offering no guarantee that the encrypted files will be released. In this incident, the email address for payment validation was shut down by the email provider, so payment is especially unlikely to lead to data recovery. According to one NCCIC stakeholder, the below sites are C2 payment sites for this activity. These sites are not included in the CSV package as IOCs.
NCCIC recommends that organizations coordinate with their security vendors to ensure appropriate coverage for this threat. Because there is overlap between the WannaCry and Petya activities, many of the available rulesets can protect against both malware strains when appropriately implemented. The following rulesets provided in publically available sources may help detect this activity:
- sid:2001569, “ET SCAN Behavioral Unusual Port 445 traffic Potential Scan or Infection”
- sid:2012063, “ET NETBIOS Microsoft SRV2.SYS SMB Negotiate ProcessID? Function Table Dereference (CVE-2009-3103)”
- sid:2024297, “ET CURRENT_EVENTS ETERNALBLUE Exploit M2 MS17-010”
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.
- Utilize host-based firewalls and block workstation-to-workstation communications.
Recommendations for Network Protection
- Disable SMBv1 and
- Block 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-CERT’s Alert on The Increasing Threat to Network Infrastructure Devices and Recommended Mitigations  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.
General Advice for Defending Against Ransomware
Precautionary measures to mitigate ransomware threats include:
- Ensure anti-virus software is up-to-date.
- Implement a data backup 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 software—especially free software—from sites you know and trust.
- Enable automated patches for your operating system and Web browser.
DHS encourages recipients who identify the use of tools or techniques discussed in this document to report information to DHS or law enforcement immediately. To request incident response resources or technical assistance, contact DHS’s National Cybersecurity and Communications Integration Center (NCCIC) at NCCICcustomerservice@hq.dhs.gov or 888-282-0870. Cyber crime incidents can also be reported to the Internet Crime Complaint Center (IC3) at https://www.ic3.gov/default.aspx.
-  Bleeping Computer: Email Provider Shuts Down Petya Inbox Preventing Victims From Recovering Files
-  Emerging Threats 2001569
-  Emerging Threats 2012063
-  Emerging Threats 2024297
-  Microsoft: Security Bulletin MS17-010
-  US-CERT: The Increasing Threat to Network Infrastructure Devices and Recommended Mitigations
-  F-Secure: (Eternal) Petya from a Developer’s Perspective
-  Microsoft |TechNet: New ransomware, old techniques: Petya adds worm capabilities
-  US-CERT: Ransomware and Recent Variants
- July 1, 2017: Initial version