T1521.002Not expressible in SigmaMOBILE

Asymmetric Cryptography

Command and ControlAndroid, iOS

Where this stands

No Sigma rule can address this — the telemetry MITRE names has no Sigma logsource behind it.

Sigma has no logsource taxonomy for mobile platforms. MITRE's telemetry here is mobile EDR and device APIs, which no Sigma rule can address.

What the technique is

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 that should not be distributed. Due to how asymmetric algorithms work, 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, ElGamal, and ECDSA. 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.

Read it on attack.mitre.org

What MITRE says you would watch

AN1762
An application generates, imports, or accesses asymmetric keypairs (e.g., RSA/ECC), uses a public key to encrypt outbound data or establish encrypted sessions, and transmits resulting ciphertext in structured communication patterns. Detection correlates keypair lifecycle activity + asymmetric crypto API usage + data transformation + background execution context + network transmission, especially when inconsistent with expected application functionality.
AN1763
Indirect evidence of asymmetric cryptographic channel usage inferred through key exchange-like network patterns and application background execution behavior, where direct observation of keypair operations is limited. Detection correlates app entitlement posture + background execution + asymmetric handshake patterns + subsequent encrypted communication.