zilinlin/RFC2PSM huggingface dataset:
Section 5. Security Considerations

The security of user data passed over the tunneled PPP connection is
   addressed by PPP, as is authentication of the PPP peers.
   Because the PPTP control channel messages are neither authenticated
   nor integrity protected, it might be possible for an attacker to
   hijack the underlying TCP connection.  It is also possible to
   manufacture false control channel messages and alter genuine messages
   in transit without detection.
   The GRE packets forming the tunnel itself are not cryptographically
   protected.  Because the PPP negotiations are carried out over the
   tunnel, it may be possible for an attacker to eavesdrop on and modify
   those negotiations.
   Unless the PPP payload data is cryptographically protected, it can be
   captured and read or modified.
Section 6. Authors' Addresses

Kory Hamzeh
   Ascend Communications
   1275 Harbor Bay Parkway
   Alameda, CA 94502
   EMail: kory@ascend.com
   Gurdeep Singh Pall
   Microsoft Corporation
   Redmond, WA
   EMail: gurdeep@microsoft.com
   William Verthein
   U.S. Robotics/3Com
   Jeff Taarud
   Copper Mountain Networks
   W. Andrew Little
   ECI Telematics
   Glen Zorn
   Microsoft Corporation
   Redmond, WA
   EMail: glennz@microsoft.com
Section 7. References

[1]  Hanks, S., Li, T., Farinacci, D. and P. Traina, "Generic Routing
   [2]  Hanks, S., Li, T., Farinacci, D. and P. Traina, "Generic Routing
   [3]  Lloyd, B. and W. Simpson, "PPP Authentication Protocols", RFC
        1334, October 1992.
   [4]  Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
        September 1981.
   [6]  Reynolds, J. and J. Postel, "Assigned Numbers", STD 2, RFC 1700,
        October 1994.  See also: http://www.iana.org/numbers.html
   [7]  Simpson, W., editor, "The Point-to-Point Protocol (PPP)", STD
   [8]  Ethertype for PPP, Reserved with Xerox Corporation.
   [9]  Simpson, W., "PPP Challenge Handshake Authentication Protocol
   [10] Blunk, L. and J Vollbrecht, "PPP Extensible Authentication
   [11] Stevens, R., "TCP/IP Illustrated, Volume 1", p. 300, Addison-
        Wesley, 1994.
   [12] Bradner, S., "Key words for use in RFCs to Indicate Requirement
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