Standard Cryptographic Protocol
Adversaries may explicitly employ a known encryption algorithm to conceal command and control traffic rather than relying on any inherent protections provided by a communication protocol. Despite the use of a secure algorithm, these implementations may be vulnerable to reverse engineering if necessary secret keys are encoded and/or generated within malware samples/configuration files.
|3PARA RAT||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. |
|adbupd||adbupd contains a copy of the OpenSSL library to encrypt C2 traffic. |
|ADVSTORESHELL||A variant of ADVSTORESHELL encrypts some C2 with 3DES and RSA. |
|APT33||APT33 has used AES for encryption of command and control traffic. |
|Azorult||Azorult can encrypt C2 traffic using XOR.  |
|BISCUIT||BISCUIT uses SSL for encrypting C2 communications. |
|Bisonal||Some Bisonal samples encrypt C2 communications with RC4. |
|BRONZE BUTLER||BRONZE BUTLER has used RC4 encryption (for Datper malware) and AES (for xxmm malware) to obfuscate HTTP traffic. |
|CallMe||CallMe uses AES to encrypt C2 traffic. |
|Carbanak||Carbanak encrypts the message body of HTTP traffic with RC2 (in CBC mode) and Base64 encoding.  |
|Chaos||Chaos provides a reverse shell connection on 8338/TCP, encrypted via AES. |
|ChChes||ChChes can encrypt C2 traffic with AES.  |
|CHOPSTICK||CHOPSTICK encrypts C2 communications with RC4 as well as TLS. |
|Cobalt Group||Cobalt Group has used the Plink utility to create SSH tunnels. |
|Comnie||Comnie encrypts command and control communications with RC4. |
|Daserf||Daserf uses RC4 encryption to obfuscate HTTP traffic. |
|Dipsind||Dipsind encrypts C2 data with AES256 in ECB mode. |
|Downdelph||Downdelph uses RC4 to encrypt C2 responses. |
|Dridex||Dridex has encrypted traffic with RSA and RC4. |
|Duqu||The Duqu command and control protocol's data stream can be encrypted with AES-CBC. |
|Elise||Elise encrypts exfiltrated data with RC4. |
|Emotet||Emotet is known to use RSA keys for encrypting C2 traffic. |
|Empire||Empire can use TLS to encrypt its C2 channel. |
|Epic||Epic encrypts commands from the C2 server using a hardcoded key. |
|FakeM||Some variants of FakeM use RC4 to encrypt C2 traffic. |
|Felismus||Some Felismus samples use AES to encrypt C2 traffic. |
|FIN6||FIN6 used the Plink command-line utility to create SSH tunnels to C2 servers. |
|FIN8||FIN8 has used the Plink utility to tunnel RDP back to C2 infrastructure. |
|FlawedAmmyy||FlawedAmmyy has used SEAL encryption during the initial C2 handshake. |
|gh0st RAT||gh0st RAT uses RC4 and XOR to encrypt C2 traffic. |
|GreyEnergy||GreyEnergy encrypts communications using AES256 and RSA-2048. |
|H1N1||H1N1 encrypts C2 traffic using an RC4 key. |
|Helminth||Helminth encrypts data sent to its C2 server over HTTP with RC4. |
|Koadic||Koadic can use SSL and TLS for communications. |
|Lazarus Group||Lazarus Group malware uses Caracachs encryption to encrypt C2 payloads. |
|LightNeuron||LightNeuron uses AES to encrypt C2 traffic. |
|Machete||Machete has relied on TLS-encrypted FTP to transfer data out of target environments. |
|MobileOrder||MobileOrder uses AES to encrypt C2 communications. |
|MoonWind||MoonWind encrypts C2 traffic using RC4 with a static key. |
|NanoCore||NanoCore uses DES to encrypt the C2 traffic. |
|NDiskMonitor||NDiskMonitor uses AES to encrypt certain information sent over its C2 channel. |
|NETEAGLE||NETEAGLE will decrypt resources it downloads with HTTP requests by using RC4 with the key "ScoutEagle." |
|Nidiran||Nidiran uses RC4 to encrypt C2 traffic. |
|OilRig||OilRig used the Plink utility and other tools to create tunnels to C2 servers. |
|PoisonIvy||PoisonIvy uses the Camellia cipher to encrypt communications. |
|POSHSPY||POSHSPY encrypts C2 traffic with AES and RSA. |
|POWERSTATS||POWERSTATS has encrypted C2 traffic with RSA. |
|POWERTON||POWERTON has used AES for encrypting C2 traffic. |
|Prikormka||Prikormka encrypts some C2 traffic with the Blowfish cipher. |
|Pupy||Pupy's default encryption for its C2 communication channel is SSL, but it also has transport options for RSA and AES. |
|QuasarRAT||QuasarRAT uses AES to encrypt network communication.  |
|RedLeaves||RedLeaves has encrypted C2 traffic with RC4, previously using keys of 88888888 and babybear. |
|Remsec||Remsec's network loader encrypts C2 traffic with RSA and RC6. |
|RIPTIDE||APT12 has used the RIPTIDE RAT, which communicates over HTTP with a payload encrypted with RC4. |
|SeaDuke||SeaDuke C2 traffic has been encrypted with RC4 and AES.  |
|ServHelper||ServHelper may set up a reverse SSH tunnel to give the attacker access to services running on the victim, such as RDP. |
|SNUGRIDE||SNUGRIDE encrypts C2 traffic using AES with a static key. |
|Stealth Falcon||Stealth Falcon malware encrypts C2 traffic using RC4 with a hard-coded key. |
|Taidoor||Taidoor uses RC4 to encrypt the message body of HTTP content. |
|Tropic Trooper||Tropic Trooper uses SSL to connect to C2 servers. |
|UPPERCUT||Some versions of UPPERCUT have used the hard-coded string “this is the encrypt key” for Blowfish encryption when communicating with a C2. Later versions have hard-coded keys uniquely for each C2 address. |
|Volgmer||Some Volgmer variants use SSL to encrypt C2 communications. |
|XTunnel||XTunnel uses SSL/TLS and RC4 to encrypt traffic.  |
|Zebrocy||Zebrocy uses SSL and AES ECB for encrypting C2 communications.  |
|ZeroT||ZeroT has used RC4 to encrypt C2 traffic.  |
|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.|
|SSL/TLS Inspection||SSL/TLS inspection can be used to see the contents of encrypted sessions to look for network-based indicators of malware communication protocols.|
SSL/TLS inspection is one way of detecting command and control traffic within some encrypted communication channels.  SSL/TLS inspection does come with certain risks that should be considered before implementing to avoid potential security issues such as incomplete certificate validation. 
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. 
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. 
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