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T1071.003 Mail Protocols

Adversaries may communicate using application layer protocols associated with electronic mail delivery to avoid detection/network filtering by blending in with existing traffic. Commands to the remote system, and often the results of those commands, will be embedded within the protocol traffic between the client and server.

Protocols such as SMTP/S, POP3/S, and IMAP that carry electronic mail may be very common in environments. Packets produced from these protocols may have many fields and headers in which data can be concealed. Data could also be concealed within the email messages themselves. An adversary may abuse these protocols to communicate with systems under their control within a victim network while also mimicking normal, expected traffic.

Item Value
ID T1071.003
Sub-techniques T1071.001, T1071.002, T1071.003, T1071.004
Tactics TA0011
Platforms Linux, Windows, macOS
Version 1.0
Created 15 March 2020
Last Modified 21 October 2020

Procedure Examples

ID Name Description
S0331 Agent Tesla Agent Tesla has used SMTP for C2 communications.789
G0007 APT28 APT28 has used IMAP, POP3, and SMTP for a communication channel in various implants, including using self-registered Google Mail accounts and later compromised email servers of its victims.1727
G0050 APT32 APT32 has used email for C2 via an Office macro.2512
S0337 BadPatch BadPatch uses SMTP for C2.23
S0351 Cannon Cannon uses SMTP/S and POP3/S for C2 communications by sending and receiving emails.14
S0023 CHOPSTICK Various implementations of CHOPSTICK communicate with C2 over SMTP and POP3.24
S0126 ComRAT ComRAT can use email attachments for command and control.15
S0137 CORESHELL CORESHELL can communicate over SMTP and POP3 for C2.1716
S0477 Goopy Goopy has the ability to use a Microsoft Outlook backdoor macro to communicate with its C2.12
S0201 JPIN JPIN can send email over SMTP.11
G0094 Kimsuky Kimsuky has used e-mail to send exfiltrated data to C2 servers.29
S0395 LightNeuron LightNeuron uses SMTP for C2.2
S0247 NavRAT NavRAT uses the email platform, Naver, for C2 communications, leveraging SMTP.10
S0138 OLDBAIT OLDBAIT can use SMTP for C2.17
S0495 RDAT RDAT can use email attachments for C2 communications.13
S0125 Remsec Remsec is capable of using SMTP for C2.456
G0083 SilverTerrier SilverTerrier uses SMTP for C2 communications.26
S1042 SUGARDUMP A SUGARDUMP variant used SMTP for C2.3
G0010 Turla Turla has used multiple backdoors which communicate with a C2 server via email attachments.28
S0251 Zebrocy Zebrocy uses SMTP and POP3 for C2.181419202122

Mitigations

ID Mitigation Description
M1031 Network Intrusion Prevention Network intrusion detection and prevention systems that use network signatures to identify traffic for specific adversary malware can be used to mitigate activity at the network level.

Detection

ID Data Source Data Component
DS0029 Network Traffic Network Traffic Content

References

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  13. Falcone, R., Lee, B. (2018, November 20). Sofacy Continues Global Attacks and Wheels Out New ‘Cannon’ Trojan. Retrieved November 26, 2018. ↩↩

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  15. Anthe, C. et al. (2015, October 19). Microsoft Security Intelligence Report Volume 19. Retrieved December 23, 2015. ↩

  16. FireEye. (2015). APT28: A WINDOW INTO RUSSIA’S CYBER ESPIONAGE OPERATIONS?. Retrieved August 19, 2015. ↩↩↩

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  23. ESET. (2016, October). En Route with Sednit - Part 2: Observing the Comings and Goings. Retrieved November 21, 2016. ↩

  24. Dahan, A. (2017, May 24). OPERATION COBALT KITTY: A LARGE-SCALE APT IN ASIA CARRIED OUT BY THE OCEANLOTUS GROUP. Retrieved November 5, 2018. ↩

  25. Unit42. (2016). SILVERTERRIER: THE RISE OF NIGERIAN BUSINESS EMAIL COMPROMISE. Retrieved November 13, 2018. ↩

  26. NSA, CISA, FBI, NCSC. (2021, July). Russian GRU Conducting Global Brute Force Campaign to Compromise Enterprise and Cloud Environments. Retrieved July 26, 2021. ↩

  27. Crowdstrike. (2020, March 2). 2020 Global Threat Report. Retrieved December 11, 2020. ↩

  28. CISA, FBI, CNMF. (2020, October 27). https://us-cert.cisa.gov/ncas/alerts/aa20-301a. Retrieved November 4, 2020. ↩