Technique:  Non-Application Layer Protocol
Anchor has used ICMP in C2 communications.
An It downloader establishes SOCKS5 connections for its initial C2.
Aria-body has used TCP in C2 communications.
AuTo Stealer can use TCP to communicate with command and control servers.
It has used EarthWorm for network tunneling with a SOCKS5 server and port transfer functionalities.
Bandook has a command built in to use a raw TCP socket.
Bisonal has used raw sockets for network communication.
It has used TCP for C2 communications.
Brute Ratel C4 has the ability to use TCP for external C2.
BUBBLEWRAP can communicate using SOCKS.
During C0021, the threat actors used TCP for some C2 communications.
Carbon uses TCP and UDP for C2.
Clambling has the ability to use TCP and UDP for communication.
Cobalt Strike can be configured to use TCP, ICMP, and UDP for C2 communications.
Crimson uses a custom TCP protocol for C2.
Cryptoistic can use TCP in communications with C2.
Derusbi binds to a raw socket on a random source port between 31800 and 31900 for C2.
Drovorub can use TCP to communicate between its agent and client modules.
Some variants of FakeM use SSL to communicate with C2 servers.
It has used Metasploit Bind and Reverse TCP stagers.
FunnyDream can communicate with C2 over TCP and UDP.
Gelsemium has the ability to use TCP and UDP in C2 communications.
gh0st RAT has used an encrypted protocol within TCP segments to communicate with the C2.
It has used TCP for C2.
HiddenWasp communicates with a simple network protocol over TCP.
InvisiMole has used TCP to download additional modules.
KEYPLUG can use TCP and KCP (KERN Communications Protocol) over UDP for C2 communication.
LookBack uses a custom binary protocol over sockets for C2 communications.
MacMa has used a custom JSON-based protocol for its C&C communications.
Mafalda can use raw TCP for C2.
It has used TCP for C2.
metaMain can establish an indirect and raw TCP socket-based connection to the C2 server.
Metamorfo has used raw TCP for C2.
Mis-Type network traffic can communicate over a raw socket.
Misdat network traffic communicates over a raw socket.
MoonWind completes network communication via raw sockets.
Mythic supports WebSocket and TCP-based C2 profiles.
Nebulae can use TCP in C2 communications.
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.
NETWIRE can use TCP in C2 communications.
During Operation Wocao, threat actors used a custom protocol for command and control.
OSX_OCEANLOTUS.D has used a custom binary protocol over port 443 for C2 traffic.
Pay2Key has sent its public key to the C2 server over TCP.
The Penquin C2 mechanism is based on TCP and UDP packets.
PHOREAL communicates via ICMP for C2.
PingPull variants have the ability to communicate with C2 servers using ICMP or TCP.
The PipeMon communication module can use a custom protocol based on TLS over TCP.
It has used the Intel® Active Management Technology (AMT) Serial-over-LAN (SOL) channel for command and control.
PlugX can be configured to use raw TCP or UDP for command and control.
QakBot has the ability use TCP to send or receive C2 packets.
QuasarRAT can use TCP for C2 communication.
QUIETEXIT can establish a TCP connection as part of its initial connection to the C2.
RainyDay can use TCP in C2 communications.
RARSTONE uses SSL to encrypt its communication with its C2 server.
RCSession has the ability to use TCP and UDP in C2 communications.
Some Reaver variants use raw TCP for C2.
The Regin malware platform can use ICMP to communicate between infected computers.
Remsec is capable of using ICMP, TCP, and UDP for C2.
RotaJakiro uses a custom binary protocol using a type, length, value format over TCP.
Royal establishes a TCP socket for C2 communication using the API WSASocketW.
Sardonic can communicate with actor-controlled C2 servers by using a custom little-endian binary protocol.
SDBbot has the ability to communicate with C2 with TCP over port 443.
ShadowPad has used UDP for C2 communications.
SombRAT has the ability to use TCP sockets to send data and ICMP to ping the C2 server.
SUGARUSH has used TCP for C2.
Taidoor can use TCP for C2 communications.
TSCookie can use ICMP to receive information on the destination server.
Umbreon provides access to the system via SSH or any other protocol that uses PAM to authenticate.
Uroburos can communicate through custom methodologies for UDP,  ICMP, and TCP that use distinct sessions to ride over the legitimate protocols.
WarzoneRAT can communicate with its C2 server via TCP over port 5200.
WellMail can use TCP for C2 communications.
WINDSHIELD C2 traffic can communicate via TCP raw sockets.
Winnti for Linux has used ICMP, custom TCP, and UDP in outbound communications.
Winnti for Windows can communicate using custom TCP.