Standard Non-Application Layer Protocol
Use of a standard non-application layer protocol for communication between host and C2 server or among infected hosts within a network. The list of possible protocols is extensive.  Specific examples include use of network layer protocols, such as the Internet Control Message Protocol (ICMP), transport layer protocols, such as the User Datagram Protocol (UDP), session layer protocols, such as Socket Secure (SOCKS), as well as redirected/tunneled protocols, such as Serial over LAN (SOL).
ICMP communication between hosts is one example. Because ICMP is part of the Internet Protocol Suite, it is required to be implemented by all IP-compatible hosts;  however, it is not as commonly monitored as other Internet Protocols such as TCP or UDP and may be used by adversaries to hide communications.
|Filter Network Traffic||Filter network traffic to prevent use of protocols across the network boundary that are unnecessary.|
|Network Intrusion Prevention||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.|
|Network Segmentation||Properly configure firewalls and proxies to limit outgoing traffic to only necessary ports and through proper network gateway systems. Also ensure hosts are only provisioned to communicate over authorized interfaces.|
If NETEAGLE does not detect a proxy configured on the infected machine, it will send beacons via UDP/6000. Also, after retrieving a C2 IP address and Port Number, NETEAGLE will initiate a TCP connection to this socket. The ensuing connection is a plaintext C2 channel in which commands are specified by DWORDs.
Analyze network traffic for ICMP messages or other protocols that contain abnormal data or are not normally seen within or exiting the network.
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. 
Monitor and investigate API calls to functions associated with enabling and/or utilizing alternative communication channels.
- Wikipedia. (n.d.). List of network protocols (OSI model). Retrieved December 4, 2014.
- Microsoft. (n.d.). Internet Control Message Protocol (ICMP) Basics. Retrieved December 1, 2014.
- Dunwoody, M., et al. (2018, November 19). Not So Cozy: An Uncomfortable Examination of a Suspected APT29 Phishing Campaign. Retrieved November 27, 2018.
- Moran, N., et al. (2014, November 21). Operation Double Tap. Retrieved January 14, 2016.
- FireEye Threat Intelligence. (2015, December 1). China-based Cyber Threat Group Uses Dropbox for Malware Communications and Targets Hong Kong Media Outlets. Retrieved December 4, 2015.
- ESET. (2017, March 30). Carbon Paper: Peering into Turla’s second stage backdoor. Retrieved November 7, 2018.
- Huss, D.. (2016, March 1). Operation Transparent Tribe. Retrieved June 8, 2016.
- Fidelis Cybersecurity. (2016, February 29). The Turbo Campaign, Featuring Derusbi for 64-bit Linux. Retrieved March 2, 2016.
- Sanmillan, I. (2019, May 29). HiddenWasp Malware Stings Targeted Linux Systems. Retrieved June 24, 2019.
- Gross, J. (2016, February 23). Operation Dust Storm. Retrieved September 19, 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.
- Carr, N.. (2017, May 14). Cyber Espionage is Alive and Well: APT32 and the Threat to Global Corporations. Retrieved June 18, 2017.
- Kaplan, D, et al. (2017, June 7). PLATINUM continues to evolve, find ways to maintain invisibility. Retrieved February 19, 2018.
- Dell SecureWorks Counter Threat Unit Threat Intelligence. (2015, August 5). Threat Group-3390 Targets Organizations for Cyberespionage. Retrieved August 18, 2018.
- Grunzweig, J. and Miller-Osborn, J. (2017, November 10). New Malware with Ties to SunOrcal Discovered. Retrieved November 16, 2017.
- Kaspersky Lab's Global Research and Analysis Team. (2014, November 24). THE REGIN PLATFORM NATION-STATE OWNAGE OF GSM NETWORKS. Retrieved December 1, 2014.
- Symantec Security Response. (2016, August 8). Backdoor.Remsec indicators of compromise. Retrieved August 17, 2016.
- Kaspersky Lab's Global Research & Analysis Team. (2016, August 9). The ProjectSauron APT. Retrieved August 17, 2016.
- Gardiner, J., Cova, M., Nagaraja, S. (2014, February). Command & Control Understanding, Denying and Detecting. Retrieved April 20, 2016.