Executive Summary

• SGI observed an attempted unauthorized injection of an SSH key, originating from IP address 101.227.79.215 in China.
• This activity targets Linux/Unix systems and potentially network devices that rely on SSH for remote administration.
• The likely objective is to gain unauthorized access to systems and enable lateral movement within the network.
• The business risk is high due to potential data breaches, system compromise, and disruption of services.
• We anticipate attackers will continue to leverage compromised or weak credentials to inject malicious SSH keys, emphasizing the need for proactive monitoring.

Observed Activity (SGI Sensors)

An SGI sensor detected suspicious network activity originating from 101.227.79.215, associated with AS4812 (China Telecom). The traffic consisted of a TCP connection carrying a payload identified as a potentially malicious SSH authorized key injection attempt. The destination port was not explicitly captured, but given the nature of the attack, it is likely port 22. VirusTotal analysis confirms the payload’s malicious nature.

Malware/Technique Overview

The detected malware family, identified as ‘20251029-214501-9f87ad2128a6-1-redir__root__ssh_authorized_keys’, suggests an attempt to modify the authorized_keys file in the root user’s SSH directory. This technique allows an attacker to gain persistent, password-less access to the compromised system.

Initial access is likely achieved through:

• Compromised Credentials: Brute-forcing or credential stuffing attacks targeting SSH accounts.
• Exploitation of Vulnerabilities: Exploiting known vulnerabilities in SSH or related services.

Typical targets include:

• Linux/Unix servers: Servers hosting critical applications or data.
• Network devices: Routers, switches, and firewalls that use SSH for management.

MITRE ATT&CK Mapping:

• T1190 – Exploit Public-Facing Application
• T1110 – Brute Force
• T1078 – Valid Accounts
• T1098.004 – Account Manipulation: SSH Authorized Keys
• T1059.004 – Command and Scripting Interpreter: Unix Shell
• T1021.004 – Remote Services: SSH

VirusTotal Snapshot

VirusTotal analysis shows that 29 vendors flagged the sample as malicious, while 33 vendors did not detect it. While the detection rate is not overwhelming, the file’s aliases and structure strongly suggest malicious intent.

• Malicious: 29
• Undetected: 33
• Harmless: 0

Notable vendor detections (example; results may vary):
Due to the sensitivity of naming specific vendors and the variability of detection results, this section avoids making definitive statements about specific vendor detections.

• VirusTotal Sample

Indicators of Compromise (IoCs)

Retention Recommendation: Monitor these IoCs for at least 90 days.

Detection & Hunting

Splunk SPL:

index=* src_ip=101.227.79.0/24  |  regex _raw="ssh-rsa AAAA[0-9A-Za-z+/]+[=]{0,3}" | table _time, src_ip, _raw

This query searches for SSH traffic originating from the identified IP range and containing SSH RSA public key patterns. Adjust the index and regex as needed for your environment.

Elastic/Kibana KQL:

source.ip : 101.227.79.0/24 AND message : "ssh-rsa AAAA*"

This query searches for logs where the source IP is within the specified range and the log message contains a string matching an SSH RSA public key. This may need to be tailored to your specific logging patterns.

Wazuh/OSSEC Rule Idea:

  5700 
  101.227.79.0/24
  Possible SSH Key Injection from China Telecom IP.

This rule triggers a level 7 alert if an SSH login attempt originates from the specified IP range. Remember to adapt the IP range as required.

Containment, Eradication & Recovery

1. Isolation: Immediately isolate any affected systems from the network to prevent further lateral movement.
2. Blocking: Block the source IP address (101.227.79.215) at the firewall level.
3. Scanning: Perform a thorough scan of all systems for unauthorized SSH keys. Check the authorized_keys files in user home directories (~/.ssh/authorized_keys) and the root account (/root/.ssh/authorized_keys).
4. Reimaging: If compromise is confirmed, reimage affected systems from a known-good backup or image.
5. Credential Resets: Reset passwords for all user accounts on affected systems, especially privileged accounts.

Inform IT and leadership about the incident and the steps taken. Preserve system logs and network traffic for forensic analysis.

Hardening & Preventive Controls

• Multi-Factor Authentication (MFA): Enforce MFA for all SSH logins (NIST CSF PR.AC-1, CIS Control 6).
• EDR Tuning: Configure Endpoint Detection and Response (EDR) solutions to detect unauthorized changes to SSH configuration files (NIST CSF DE.CM-1, CIS Control 10).
• Network Segmentation: Implement network segmentation to limit the blast radius of a potential compromise (NIST CSF PR.DS-5, CIS Control 14).
• Least Privilege: Enforce the principle of least privilege for all user accounts (NIST CSF PR.AC-3, CIS Control 5).
• Patch SLAs: Establish and enforce strict patch SLAs for all systems, especially those exposed to the internet (NIST CSF PR.PT-1, CIS Control 7).
• Disable Password Authentication: Where possible, disable password authentication for SSH and rely on key-based authentication (CIS Critical Security Controls).
• Regularly Rotate SSH Keys: Implement a process for regularly rotating SSH keys to minimize the impact of compromised keys.

Business Impact & Risk Outlook

A successful SSH key injection can lead to significant operational disruption, data breaches, and reputational damage. Legal and regulatory compliance may also be affected, depending on the sensitivity of the data accessed.

We anticipate an increase in SSH-related attacks over the next 3-6 months as attackers continue to target remote access vectors. Organizations should prioritize hardening their SSH configurations and implementing proactive monitoring to detect and respond to these threats.

Appendix

Assumptions & Data Gaps:

• We assume the destination port for the attempted SSH key injection was port 22, the default SSH port.
• We lack specific details on the injected SSH key’s contents.
• The sensor name is missing from the provided data.

References:

• VirusTotal Sample

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