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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.1

Item Value
ID T1071.003
Sub-techniques T1071.001, T1071.002, T1071.003, T1071.004, T1071.005
Tactics TA0011
Platforms Linux, Network Devices, Windows, macOS
Version 1.2
Created 15 March 2020
Last Modified 24 October 2025

Procedure Examples

ID Name Description
S0331 Agent Tesla Agent Tesla has used SMTP for C2 communications.242523
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.133
G0050 APT32 APT32 has used email for C2 via an Office macro.3226
S0337 BadPatch BadPatch uses SMTP for C2.6
S0351 Cannon Cannon uses SMTP/S and POP3/S for C2 communications by sending and receiving emails.15
S0023 CHOPSTICK Various implementations of CHOPSTICK communicate with C2 over SMTP and POP3.7
S0126 ComRAT ComRAT can use email attachments for command and control.3
G1052 Contagious Interview Contagious Interview has utilized email notifications from malware distribution servers to track victim engagement.35
S0137 CORESHELL CORESHELL can communicate over SMTP and POP3 for C2.15
S0477 Goopy Goopy has the ability to use a Microsoft Outlook backdoor macro to communicate with its C2.26
S1152 IMAPLoader IMAPLoader uses the IMAP email protocol for command and control purposes.27
S0201 JPIN JPIN can send email over SMTP.9
G0094 Kimsuky Kimsuky has used e-mail to send exfiltrated data to C2 servers.34
S0395 LightNeuron LightNeuron uses SMTP for C2.4
S1142 LunarMail LunarMail can communicates with C2 using email messages via the Outlook Messaging API (MAPI).29
S0247 NavRAT NavRAT uses the email platform, Naver, for C2 communications, leveraging SMTP.14
S1090 NightClub NightClub can use emails for C2 communications.21
S0138 OLDBAIT OLDBAIT can use SMTP for C2.1
S1173 PowerExchange PowerExchange can receive and send back the results of executed C2 commands through email.22
S0495 RDAT RDAT can use email attachments for C2 communications.20
S0125 Remsec Remsec is capable of using SMTP for C2.13101112
G0083 SilverTerrier SilverTerrier uses SMTP for C2 communications.31
S1042 SUGARDUMP A SUGARDUMP variant used SMTP for C2.28
G0010 Turla Turla has used multiple backdoors which communicate with a C2 server via email attachments.30
S0022 Uroburos Uroburos can use custom communications protocols that ride over SMTP.8
S0251 Zebrocy Zebrocy uses SMTP and POP3 for C2.1915171816

Mitigations

ID Mitigation Description
M1037 Filter Network Traffic Limit the ability of servers and critical systems to initiate outbound email communications. Filtering SMTP/IMAP/POP3 traffic to only trusted mail servers reduces the risk of attackers using compromised systems to exfiltrate data via email or to receive commands from attacker-controlled email accounts.
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.

References

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

  34. Aleksandar Milenkoski, Sreekar Madabushi, Kenneth Kinion. (2025, September 4). Contagious Interview | North Korean Threat Actors Reveal Plans and Ops by Abusing Cyber Intel Platforms. Retrieved October 20, 2025. ↩