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sftp threat model - perplexity

Here is a threat model for a machine-to-machine SFTP connection used for file exchange, based on the STRIDE methodology and aligned with MITRE ATT&CK techniques.

Threat Model: Machine-to-Machine SFTP File Exchange

Context: Secure File Transfer Protocol (SFTP) is used for automated, secure file transfers between machines. It relies on SSH for encryption and authentication to protect data in transit.

STRIDE Categories Applied to SFTP Connection

1. Spoofing (Identity Forgery)

Threats:

  • An attacker impersonates a legitimate machine or user to gain unauthorized SFTP access.
  • Weak or compromised SSH keys/passwords can enable spoofing.
  • Man-in-the-Middle (MitM) attacks on SSH handshake. MITRE Techniques:
  • T1078 (Valid Accounts): Use of stolen credentials or keys to authenticate.
  • T1556 (Modify Authentication Process): Attacker modifies authentication to bypass controls.

2. Tampering (Data Manipulation)

Threats:

  • Unauthorized modification of files during transfer or on the server due to insufficient integrity checks.
  • Alteration of SFTP server or client configurations to introduce vulnerabilities. MITRE Techniques:
  • T1565 (Data Manipulation): Changing files in transit or at rest.
  • T1609 (Container and Resource Hijacking): Manipulating containerized SFTP setups or environment.

3. Repudiation (Denial of an Action)

Threats:

  • Lack of adequate logging makes it possible for an entity to deny performing file transfers or modifications.
  • Insufficient audit trails on file uploads/downloads. MITRE Techniques:
  • T1078 (Valid Accounts): Since legitimate credentials might be used, evidence can be hard to distinguish.
  • T1622 (Indirect Command Execution): Actions performed via automated scripts without user accountability.

4. Information Disclosure (Data Exposure)

Threats:

  • Exposure of sensitive data if encryption is misconfigured or disabled.
  • Compromise of SSH keys leading to unauthorized decryption of traffic.
  • Server misconfigurations allowing directory listing or unauthorized file access. MITRE Techniques:
  • T1537 (Transfer Data to Cloud Account): Exfiltrated data via compromised SFTP.
  • T1040 (Network Sniffing): Intercepting unencrypted SFTP traffic if encryption is weak or bypassed.

5. Denial of Service (Service Disruption)

Threats:

  • Flooding SFTP server with connection requests to exhaust resources.
  • Exploiting server misconfigurations leading to crashes or lockouts. MITRE Techniques:
  • T1499 (Endpoint Denial of Service): Overloading SFTP endpoint.
  • T1022 (Data Encrypted for Impact): Encrypting data or system components making SFTP ineffective.

6. Elevation of Privilege (Unauthorized Access Rights Increase)

Threats:

  • Exploiting vulnerabilities in SSH or SFTP server software to gain higher privileges.
  • Improper file permissions allowing access escalation. MITRE Techniques:
  • T1068 (Exploitation for Privilege Escalation): Attacker exploits flaws to gain root/admin on SFTP server.
  • T1617 (Access Token Manipulation): Leveraging valid tokens for privilege escalation.

Additional Considerations for Machine-to-Machine SFTP

  • Authentication Methods: Prefer public key authentication over passwords to mitigate spoofing risks. Rotate and protect SSH keys diligently[1][3].
  • Configuration Hardening: Ensure strict file and directory permissions. Disable unused SSH/SFTP features and monitor configurations for unauthorized changes[1][7].
  • Logging and Monitoring: Maintain comprehensive logs of file transfer operations and SSH sessions to mitigate repudiation and facilitate incident response[1][4].
  • Patch Management: Regularly update SSH and SFTP server software to fix known vulnerabilities that could be exploited for tampering or privilege elevation[1].
  • Network Controls: Use firewall rules and IP whitelisting to restrict SFTP access to trusted machines[1][7].
  • Encryption Integrity: Employ strong SSH encryption algorithms and verify server fingerprints to prevent MitM and interception[3].

This threat model combines STRIDE with MITRE ATT&CK techniques related to credential use, data manipulation, denial of service, and privilege escalation consistent with risks intrinsic to SFTP-based automated file exchange between machines.

If you want, I can also provide a tabular or more detailed report for each STRIDE category with specific mitigations. Would you like that?

[1] https://www.kiteworks.com/secure-file-transfer/sftp-vulnerabilities/
[2] https://www.iriusrisk.com/resources-blog/threat-modeling-methodology-stride
[3] https://www.kiteworks.com/secure-file-transfer/sftp-security/
[4] https://www.jit.io/resources/app-security/stride-threat-model-a-complete-guide
[5] https://www.reddit.com/r/AskTechnology/comments/icmfwp/is_sftp_really_the_most_secure_way_of/
[6] https://ctid.mitre.org/projects/threat-modeling-with-attack/
[7] https://jadaptive.com/push-sftp/advanced-sftp-server-configuration-and-security-best-practices/
[8] https://attack.mitre.org/techniques/T1570/
[9] https://www.jscape.com/blog/why-more-it-professionals-are-switching-from-basic-sftp-server-software-to-mft
[10] https://www.practical-devsecops.com/types-of-threat-modeling-methodology/

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