Standard Cryptographic Protocol
|Standard Cryptographic Protocol|
|Tactic||Command and Control|
|Platform||Linux, macOS, Windows|
|Data Sources||Packet capture, Netflow/Enclave netflow, Malware reverse engineering, Process use of network, Process monitoring, SSL/TLS inspection|
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.
- APT34 used the Plink utility and other tools to create tunnels to C2 servers.1
- BRONZE BUTLER has used RC4 encryption (for Datper malware) and AES (for xxmm malware) to obfuscate HTTP traffic.2
- FIN6 used the Plink command-line utility to create SSH tunnels to C2 servers.3
- Lazarus Group malware uses Caracachs encryption to encrypt C2 payloads.4
- Stealth Falcon malware encrypts C2 traffic using RC4 with a hard-coded key.5
- Taidoor uses RC4 to encrypt the message body of HTTP content.6
- 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.7
- A variant of ADVSTORESHELL encrypts some C2 with 3DES and RSA.8
- CHOPSTICK encrypts C2 communications with RC4 as well as TLS.9
- CallMe uses AES to encrypt C2 traffic.10
- Carbanak encrypts the message body of HTTP traffic with RC2 and Base64 encoding.11
- ChChes can encrypt C2 traffic with AES.1213
- Daserf uses RC4 encryption to obfuscate HTTP traffic.2
- Downdelph uses RC4 to encrypt C2 responses.14
- The Duqu command and control protocol's data stream can be encrypted with AES-CBC.15
- Elise encrypts exfiltrated data with RC4.16
- Some variants of FakeM use RC4 to encrypt C2 traffic.10
- Some Felismus samples use AES to encrypt C2 traffic.17
- H1N1 encrypts C2 traffic using an RC4 key.18
- Helminth encrypts data sent to its C2 server over HTTP with RC4.19
- MobileOrder uses AES to encrypt C2 communications.10
- MoonWind encrypts C2 traffic using RC4 with a static key.20
- NETEAGLE will decrypt resources it downloads with HTTP requests by using RC4 with the key "ScoutEagle."21
- Nidiran uses RC4 to encrypt C2 traffic.22
- POSHSPY encrypts C2 traffic with AES and RSA.23
- PoisonIvy uses the Camellia cipher to encrypt communications.24
- Prikormka encrypts some C2 traffic with the Blowfish cipher.25
- APT12 has used the RIPTIDE RAT, which communicates over HTTP with a payload encrypted with RC4.26
- RedLeaves encrypts C2 traffic with RC4 using a secret key of 88888888.27
- Remsec's network loader encrypts C2 traffic with RSA and RC6.28
- SNUGRIDE encrypts C2 traffic using AES with a static key.29
- SeaDuke C2 traffic has been encrypted with RC4 and AES.3031
- Some Volgmer use SSL to encrypt C2 communications.32
- XTunnel uses SSL/TLS and RC4 to encrypt traffic.339
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.34
SSL/TLS inspection is one way of detecting command and control traffic within some encrypted communication channels.35 SSL/TLS inspection does come with certain risks that should be considered before implementing to avoid potential security issues such as incomplete certificate validation.36
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.37
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.34
- Davis, S. and Caban, D. (2017, December 19). APT34 - New Targeted Attack in the Middle East. Retrieved December 20, 2017.
- Counter Threat Unit Research Team. (2017, October 12). BRONZE BUTLER Targets Japanese Enterprises. Retrieved January 4, 2018.
- FireEye Threat Intelligence. (2016, April). Follow the Money: Dissecting the Operations of the Cyber Crime Group FIN6. Retrieved June 1, 2016.
- Novetta Threat Research Group. (2016, February 24). Operation Blockbuster: Unraveling the Long Thread of the Sony Attack. Retrieved February 25, 2016.
- 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.
- Trend Micro. (2012). The Taidoor Campaign. Retrieved November 12, 2014.
- Crowdstrike Global Intelligence Team. (2014, June 9). CrowdStrike Intelligence Report: Putter Panda. Retrieved January 22, 2016.
- Bitdefender. (2015, December). APT28 Under the Scope. Retrieved February 23, 2017.
- ESET. (2016, October). En Route with Sednit - Part 2: Observing the Comings and Goings. Retrieved November 21, 2016.
- Falcone, R. and Miller-Osborn, J.. (2016, January 24). Scarlet Mimic: Years-Long Espionage Campaign Targets Minority Activists. Retrieved February 10, 2016.
- Kaspersky Lab's Global Research and Analysis Team. (2015, February). CARBANAK APT THE GREAT BANK ROBBERY. Retrieved March 3, 2015.
- Miller-Osborn, J. and Grunzweig, J.. (2017, February 16). menuPass Returns with New Malware and New Attacks Against Japanese Academics and Organizations. Retrieved March 1, 2017.
- Nakamura, Y.. (2017, February 17). ChChes - Malware that Communicates with C&C Servers Using Cookie Headers. Retrieved March 1, 2017.
- ESET. (2016, October). En Route with Sednit - Part 3: A Mysterious Downloader. Retrieved November 21, 2016.
- Symantec Security Response. (2011, November). W32.Duqu: The precursor to the next Stuxnet. Retrieved September 17, 2015.
- Falcone, R., et al.. (2015, June 16). Operation Lotus Blossom. Retrieved February 15, 2016.
- Somerville, L. and Toro, A. (2017, March 30). Playing Cat & Mouse: Introducing the Felismus Malware. Retrieved November 16, 2017.
- Reynolds, J.. (2016, September 14). H1N1: Technical analysis reveals new capabilities – part 2. Retrieved September 26, 2016.
- Falcone, R. and Lee, B.. (2016, May 26). The OilRig Campaign: Attacks on Saudi Arabian Organizations Deliver Helminth Backdoor. Retrieved May 3, 2017.
- Miller-Osborn, J. and Grunzweig, J.. (2017, March 30). Trochilus and New MoonWind RATs Used In Attack Against Thai Organizations. Retrieved March 30, 2017.
- FireEye Labs. (2015, April). APT30 AND THE MECHANICS OF A LONG-RUNNING CYBER ESPIONAGE OPERATION. Retrieved May 1, 2015.
- DiMaggio, J.. (2016, May 17). Indian organizations targeted in Suckfly attacks. Retrieved August 3, 2016.
- Dunwoody, M.. (2017, April 3). Dissecting One of APT29’s Fileless WMI and PowerShell Backdoors (POSHSPY). Retrieved April 5, 2017.
- FireEye. (2014). POISON IVY: Assessing Damage and Extracting Intelligence. Retrieved November 12, 2014.
- Cherepanov, A.. (2016, May 17). Operation Groundbait: Analysis of a surveillance toolkit. Retrieved May 18, 2016.
- Moran, N., Oppenheim, M., Engle, S., & Wartell, R.. (2014, September 3). Darwin’s Favorite APT Group [Blog]. Retrieved November 12, 2014.
- PwC and BAE Systems. (2017, April). Operation Cloud Hopper: Technical Annex. Retrieved April 13, 2017.
- Symantec Security Response. (2016, August 8). Backdoor.Remsec indicators of compromise. Retrieved August 17, 2016.
- FireEye iSIGHT Intelligence. (2017, April 6). APT10 (MenuPass Group): New Tools, Global Campaign Latest Manifestation of Longstanding Threat. Retrieved June 29, 2017.
- Grunzweig, J.. (2015, July 14). Unit 42 Technical Analysis: Seaduke. Retrieved August 3, 2016.
- Dunwoody, M. and Carr, N.. (2016, September 27). No Easy Breach DerbyCon 2016. Retrieved October 4, 2016.
- US-CERT. (2017, November 22). Alert (TA17-318B): HIDDEN COBRA – North Korean Trojan: Volgmer. Retrieved December 7, 2017.
- Belcher, P.. (2016, July 28). Tunnel of Gov: DNC Hack and the Russian XTunnel. Retrieved August 3, 2016.
- Gardiner, J., Cova, M., Nagaraja, S. (2014, February). Command & Control Understanding, Denying and Detecting. Retrieved April 20, 2016.
- Butler, M. (2013, November). Finding Hidden Threats by Decrypting SSL. Retrieved April 5, 2016.
- Dormann, W. (2015, March 13). The Risks of SSL Inspection. Retrieved April 5, 2016.
- Fidelis Cybersecurity. (2015, August 4). Looking at the Sky for a DarkComet. Retrieved April 5, 2016.