Standard Cryptographic Protocol

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Standard Cryptographic Protocol
Technique
ID T1032
Tactic Command and Control
Platform Windows Server 2003, Windows Server 2008, Windows Server 2012, Windows XP, Windows 7, Windows 8, Windows Server 2003 R2, Windows Server 2008 R2, Windows Server 2012 R2, Windows Vista, Windows 8.1
Data Sources Packet capture, Netflow/Enclave netflow, Malware reverse engineering, Process use of network, Process monitoring, SSL/TLS inspection
Requires Network Yes

Adversaries use command and control over an encrypted channel using a known encryption protocol like HTTPS or SSL/TLS. The use of strong encryption makes it difficult for defenders to detect signatures within adversary command and control traffic.

Some adversaries may use other encryption protocols and algorithms with symmetric keys, such as RC4, that rely on encryption keys encoded into malware configuration files and not public key cryptography. Such keys may be obtained through malware reverse engineering.

Examples

  • Taidoor uses RC4 to encrypt the message body of HTTP content.1
  • Lazarus Group malware uses Caracachs encryption to encrypt C2 payloads.2
  • FIN6 used the Plink command-line utility to create SSH tunnels to C2 servers.3
  • Stealth Falcon malware encrypts C2 traffic using RC4 with a hard-coded key.4
  • APT12 has used the RIPTIDE RAT, which communicates over HTTP with a payload encrypted with RC4.5
  • PoisonIvy uses the Camellia cipher to encrypt communications.6
  • CHOPSTICK encrypts C2 communications with RC4 as well as TLS.7
  • Carbanak encrypts the message body of HTTP traffic with RC2 and Base64 encoding.8
  • NETEAGLE will decrypt resources it downloads with HTTP requests by using RC4 with the key "ScoutEagle."9
  • The Duqu command and control protocol's data stream can be encrypted with AES-CBC.10
  • SeaDuke C2 traffic has been encrypted with RC4 and AES.1112
  • 3PARA RAT command and control commands are encrypted within the HTTP C2 channel using the DES algorithm in CBC mode with a key derived from the MD5 hash of the string HYF54&%9&jkMCXuiS.13
  • Some variants of FakeM use RC4 to encrypt C2 traffic.14
  • CallMe uses AES to encrypt C2 traffic.14
  • MobileOrder uses AES to encrypt C2 communications.14
  • Elise encrypts exfiltrated data with RC4.15
  • Prikormka encrypts some C2 traffic with the Blowfish cipher.16
  • XTunnel uses SSL/TLS and RC4 to encrypt traffic.177
  • Nidiran uses RC4 to encrypt C2 traffic.18
  • Remsec's network loader encrypts C2 traffic with RSA and RC6.19
  • H1N1 encrypts C2 traffic using an RC4 key.20
  • Downdelph uses RC4 to encrypt C2 responses.21

Mitigation

Network intrusion detection and prevention systems that use network signatures to identify traffic for specific adversary malware can be used to mitigate activity at the network level. Use of encryption protocols may make typical network-based C2 detection more difficult due to a reduced ability to signature the traffic. Prior knowledge of adversary C2 infrastructure may be useful for domain and IP address blocking, but will likely not be an effective long-term solution because adversaries can change infrastructure often.22

Detection

SSL/TLS inspection is one way of detecting command and control traffic within some encrypted communication channels.23 SSL/TLS inspection does come with certain risks that should be considered before implementing to avoid potential security issues such as incomplete certificate validation.24

If malware uses encryption with symmetric keys, it may be possible to obtain the algorithm and key from samples and use them to decode network traffic to detect malware communications signatures.25

In general, analyze network data for uncommon data flows (e.g., a client sending significantly more data than it receives from a server). Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious. Analyze packet contents to detect communications that do not follow the expected protocol behavior for the port that is being used.22

References

  1. ^  Trend Micro. (2012). The Taidoor Campaign. Retrieved November 12, 2014.
  2. ^  Novetta Threat Research Group. (2016, February 24). Operation Blockbuster: Unraveling the Long Thread of the Sony Attack. Retrieved February 25, 2016.
  3. ^  FireEye Threat Intelligence. (2016, April). Follow the Money: Dissecting the Operations of the Cyber Crime Group FIN6. Retrieved June 1, 2016.
  4. ^  Marczak, B. and Scott-Railton, J.. (2016, May 29). Keep Calm and (Don’t) Enable Macros: A New Threat Actor Targets UAE Dissidents. Retrieved June 8, 2016.
  5. ^  Moran, N., Oppenheim, M., Engle, S., & Wartell, R.. (2014, September 3). Darwin’s Favorite APT Group [Blog]. Retrieved November 12, 2014.
  6. ^  FireEye. (2014). POISON IVY: Assessing Damage and Extracting Intelligence. Retrieved November 12, 2014.
  7. a b  ESET. (2016, October). En Route with Sednit - Part 2: Observing the Comings and Goings. Retrieved November 21, 2016.
  8. ^  Kaspersky Lab's Global Research and Analysis Team. (2015, February). CARBANAK APT THE GREAT BANK ROBBERY. Retrieved March 3, 2015.
  9. ^  FireEye Labs. (2015, April). APT30 AND THE MECHANICS OF A LONG-RUNNING CYBER ESPIONAGE OPERATION. Retrieved May 1, 2015.
  10. ^  Symantec Security Response. (2011, November). W32.Duqu: The precursor to the next Stuxnet. Retrieved September 17, 2015.
  11. ^  Grunzweig, J.. (2015, July 14). Unit 42 Technical Analysis: Seaduke. Retrieved August 3, 2016.
  12. ^  Dunwoody, M. and Carr, N.. (2016, September 27). No Easy Breach DerbyCon 2016. Retrieved October 4, 2016.
  13. ^  Crowdstrike Global Intelligence Team. (2014, June 9). CrowdStrike Intelligence Report: Putter Panda. Retrieved January 22, 2016.