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.
Detection Strategy for Encrypted Channel via Asymmetric Cryptography across OS Platforms
Network Intrusion Prevention: Use intrusion detection signatures to block traffic at network boundaries.
SSL/TLS Inspection: SSL/TLS inspection involves decrypting encrypted network traffic to examine its content for signs of malicious activity. This capability is crucial for detecting threats that use encryption to evade detection, such as phishing, malware, or data exfiltration. After inspection, the traffic is re-encrypted and forwarded to its destination. This mitigation can be implemented through the following measures:
Deploy SSL/TLS Inspection Appliances:
Configure Decryption Policies:
Integrate Threat Intelligence:
Integrate with Security Tools:
Implement Certificate Management:
Monitor and Tune: