Adversaries may use a connection proxy to direct network traffic between systems or act as an intermediary for network communications to a command and control server to avoid direct connections to their infrastructure. Many tools exist that enable traffic redirection through proxies or port redirection, including HTRAN, ZXProxy, and ZXPortMap. [1] Adversaries use these types of proxies to manage command and control communications, reduce the number of simultaneous outbound network connections, provide resiliency in the face of connection loss, or to ride over existing trusted communications paths between victims to avoid suspicion. Adversaries may chain together multiple proxies to further disguise the source of malicious traffic.
Adversaries can also take advantage of routing schemes in Content Delivery Networks (CDNs) to proxy command and control traffic.
| ID | Name | Description |
|---|---|---|
| G0096 | APT41 |
APT41 used a tool called CLASSFON to covertly proxy network communications.[2] |
| S0456 | Aria-body |
Aria-body has the ability to use a reverse SOCKS proxy module.[3] |
| S0347 | AuditCred | |
| S0245 | BADCALL |
BADCALL functions as a proxy server between the victim and C2 server.[5] |
| G0108 | Blue Mockingbird |
Blue Mockingbird has used frp, ssf, and Venom to establish SOCKS proxy connections.[6] |
| S0348 | Cardinal RAT |
Cardinal RAT can act as a reverse proxy.[7] |
| S0384 | Dridex |
Dridex contains a backconnect module for tunneling network traffic through a victim's computer. Infected computers become part of a P2P botnet that can relay C2 traffic to other infected peers.[8][9] |
| G0117 | Fox Kitten |
Fox Kitten has used the open source reverse proxy tools including FRPC and Go Proxy to establish connections from C2 to local servers.[10][11][12] |
| S0246 | HARDRAIN |
HARDRAIN uses the command |
| S0376 | HOPLIGHT |
HOPLIGHT has multiple proxy options that mask traffic between the malware and the remote operators.[14] |
| S0040 | HTRAN |
HTRAN can proxy TCP socket connections to obfuscate command and control infrastructure.[15][16] |
| S0283 | jRAT | |
| S0487 | Kessel |
Kessel can use a proxy during exfiltration if set in the configuration.[18] |
| S0108 | netsh |
netsh can be used to set up a proxy tunnel to allow remote host access to an infected host.[19] |
| S0198 | NETWIRE | |
| S0508 | Ngrok |
Ngrok can be used to proxy connections to machines located behind NAT or firewalls.[21][22] |
| G0116 | Operation Wocao |
Operation Wocao has used a custom proxy tool called "Agent" which has support for multiple hops.[23] |
| S0435 | PLEAD | |
| S0378 | PoshC2 |
PoshC2 contains modules that allow for use of proxies in command and control.[25] |
| S0262 | QuasarRAT |
QuasarRAT can communicate over a reverse proxy using SOCKS5.[26][27] |
| S0629 | RainyDay |
RainyDay can use proxy tools including boost_proxy_client for reverse proxy functionality.[28] |
| S0332 | Remcos |
Remcos uses the infected hosts as SOCKS5 proxies to allow for tunneling and proxying.[29] |
| G0034 | Sandworm Team |
Sandworm Team's BCS-server tool can create an internal proxy server to redirect traffic from the adversary-controlled C2 to internal servers which may not be connected to the internet, but are interconnected locally.[30] |
| S0461 | SDBbot |
SDBbot has the ability to use port forwarding to establish a proxy between a target host and C2.[31] |
| S0273 | Socksbot | |
| S0615 | SombRAT |
SombRAT has the ability to use an embedded SOCKS proxy in C2 communications.[33] |
| S0436 | TSCookie |
TSCookie has the ability to proxy communications with command and control (C2) servers.[34] |
| G0010 | Turla |
Turla RPC backdoors have included local UPnP RPC proxies.[35] |
| S0263 | TYPEFRAME |
A TYPEFRAME variant can force the compromised system to function as a proxy server.[36] |
| S0386 | Ursnif |
Ursnif has used a peer-to-peer (P2P) network for C2.[37][38] |
| S0207 | Vasport | |
| G0124 | Windigo |
Windigo has delivered a generic Windows proxy Win32/Glubteta.M. Windigo has also used multiple reverse proxy chains as part of their C2 infrastructure.[40] |
| S0117 | XTunnel |
XTunnel relays traffic between a C2 server and a victim.[41] |
| S0412 | ZxShell |
| ID | Mitigation | Description |
|---|---|---|
| M1037 | Filter Network Traffic |
Traffic to known anonymity networks and C2 infrastructure can be blocked through the use of network allow and block lists. It should be noted that this kind of blocking may be circumvented by other techniques like Domain Fronting. |
| M1031 | 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. Signatures are often for unique indicators within protocols and may be based on the specific C2 protocol used by a particular adversary or tool, and will likely be different across various malware families and versions. Adversaries will likely change tool C2 signatures over time or construct protocols in such a way as to avoid detection by common defensive tools. [43] |
| M1020 | SSL/TLS Inspection |
If it is possible to inspect HTTPS traffic, the captures can be analyzed for connections that appear to be domain fronting. |
| ID | Data Source | Data Component |
|---|---|---|
| DS0029 | Network Traffic | Network Connection Creation |
| Network Traffic Content | ||
| Network Traffic Flow |
Analyze network data for uncommon data flows (e.g., a client sending significantly more data than it receives from a server or between clients that should not or often do not communicate with one another). 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. [43]
Consider monitoring for traffic to known anonymity networks (such as Tor).