Cross-source coverage

T1573.002 / ATT&CK

Encrypted Channel: Asymmetric Cryptography

9 rules across 3 sources.

Showing deprecated rules · back to the default

From MITRE ATT&CK 19.2

Adversaries may employ a known asymmetric encryption algorithm to conceal command and control traffic rather than relying on any inherent protections provided by a communication protocol. Asymmetric cryptography, also known as public key cryptography, uses a keypair per party: one public that can be freely distributed, and one private. Due to how the keys are generated, the sender encrypts data with the receiver’s public key and the receiver decrypts the data with their private key. This ensures that only the intended recipient can read the encrypted data. Common public key encryption algorithms include RSA and ElGamal.

For efficiency, many protocols (including SSL/TLS) use symmetric cryptography once a connection is established, but use asymmetric cryptography to establish or transmit a key. As such, these protocols are classified as Asymmetric Cryptography.

Platforms
ESXi · Linux · macOS · Network Devices · Windows
Telemetry
WinEventLog:Sysmonauditd:SYSCALLlinux:sysloglinux:osquerymacos:unifiedlogesxi:vpxdesxcli:networkNSM:FlowIDS:TLSInspection

How MITRE says to detect it DET0543

Detection Strategy for Encrypted Channel via Asymmetric Cryptography across OS Platforms

Windows Analytic 1496

Processes not typically associated with encryption loading asymmetric crypto libraries (e.g., rsaenh.dll, crypt32.dll) and subsequently initiating outbound TLS/SSL connections with abnormal certificate chains or handshakes. Defender correlates process creation, module load, and unusual encrypted sessions.

  • WinEventLog:Sysmon EventCode=7
  • WinEventLog:Sysmon EventCode=3, 22

Linux Analytic 1497

Processes (e.g., bash, python, custom binaries) dynamically linking libcrypto/libssl for RSA key exchange, then creating external connections with abnormal certificate validation or handshake anomalies. Defender observes syscall traces and outbound asymmetric key exchanges from non-SSL-native processes.

  • auditd:SYSCALL execve or socket/connect system calls for processes using RSA handshake
  • linux:syslog Non-standard processes negotiating SSL/TLS key exchanges
  • linux:osquery Processes linked with libssl/libcrypto performing network activity

macOS Analytic 1498

Applications or launchd services invoking RSA or public-key routines from the Security framework, followed by outbound SSL/TLS sessions with unrecognized certs or anomalous handshakes. Defender observes unified logs of API calls and suspicious network entropy.

  • macos:unifiedlog Process invoking SecKeyCreateRandomKey or asymmetric crypto APIs
  • macos:unifiedlog TLS connections with abnormal handshake sequence or self-signed cert

ESXi Analytic 1499

VMware services (hostd, vpxa) unexpectedly negotiating asymmetric crypto sessions to external endpoints outside vCenter or update servers. Defender sees encrypted handshakes in logs inconsistent with baseline ESXi communication patterns.

  • esxi:vpxd ESXi process initiating asymmetric handshake with external host
  • esxcli:network Socket inspection showing RSA key exchange outside baseline endpoints

Network Devices Analytic 1500

Encrypted sessions detected with asymmetric key exchange anomalies on non-standard ports or with invalid/malformed certs. Defender correlates NetFlow/IPFIX with IDS/IPS detecting RSA exchanges outside expected TLS flows.

  • NSM:Flow Flow records with RSA key exchange on unexpected port
  • IDS:TLSInspection Malformed certs, incomplete asymmetric handshakes, or invalid CAs

View on attack.mitre.org ↗

splunk/security_content

5 rules
Detection Severity Format
Cisco Secure Firewall - Blacklisted SSL Certificate Fingerprint Undefined SPL
Cisco Secure Firewall - High EVE Threat Confidence Undefined SPL
Cisco Secure Firewall - Intrusion Events by Threat Activity Undefined SPL
Cisco Secure Firewall - Lumma Stealer Download Attempt Undefined SPL
Cisco Secure Firewall - Lumma Stealer Outbound Connection Attempt Undefined SPL

elastic/detection-rules

2 rules
Detection Severity Format
Openssl Client or Server Activity Medium Elastic TOML
Deprecated - Potential Non-Standard Port HTTP/HTTPS connection Low Elastic TOML

panther-labs/panther-analysis

2 rules
Detection Severity Format
GCP K8s IOCActivity Medium Panther Python
Kubernetes API Activity from Tor Exit Node Medium Panther Python

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