Techniques › T1205
T1205 Traffic Signaling
stealth · persistence · command and control — Linux, macOS, Network Devices, Windows · attack.mitre.org · JSON
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MITRE detection strategy
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analytics
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Sigma rules tagged attack.t1205
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KEV CVEs mapped here
<p>Adversaries may use traffic signaling to hide open ports or other malicious functionality used for persistence or command and control. Traffic signaling involves the use of a magic value or sequence that must be sent to a system to trigger a special response, such as opening a closed port or executing a malicious task. This may take the form of sending a series of packets with certain characteristics before a port will be opened that the adversary can use for command and control. Usually this series of packets consists of attempted connections to a predefined sequence of closed ports (i.e. Port Knocking), but can involve unusual flags, specific strings, or other unique characteristics. After the sequence is completed, opening a port may be accomplished by the host-based firewall, but could also be implemented by custom software.</p><p>Adversaries may also communicate with an already open port, but the service listening on that port will only respond to commands or trigger other malicious functionality if passed the appropriate magic value(s).</p><p>The observation of the signal packets to trigger the communication can be conducted through different methods. One means, originally implemented by Cd00r, is to use the libpcap libraries to sniff for the packets in question. Another method leverages raw sockets, which enables the malware to use ports that are already open for use by other programs.</p><p>On network devices, adversaries may use crafted packets to enable Network Device Authentication for standard services offered by the device such as telnet. Such signaling may also be used to open a closed service port such as telnet, or to trigger module modification of malware implants on the device, adding, removing, or changing malicious capabilities. Adversaries may use crafted packets to attempt to connect to one or more (open or closed) ports, but may also attempt to connect to a router interface, broadcast, and network address IP on the same port in order to achieve their goals and objectives. To enable this traffic signaling on embedded devices, adversaries must first achieve and leverage Patch System Image due to the monolithic nature of the architecture.</p><p>Adversaries may also use the Wake-on-LAN feature to turn on powered off systems. Wake-on-LAN is a hardware feature that allows a powered down system to be powered on, or woken up, by sending a magic packet to it. Once the system is powered on, it may become a target for lateral movement.</p>
KEV CVEs mapped to this technique · CTID Mappings Explorer
None. No KEV entry in the public mapping names this technique. Given that 74.7% of KEV has no mapping at all, this says more about the mapping than about the technique.
Detection strategy · ATT&CK Enterprise v19.2
- DET0524 Traffic Signaling (Port-knock / magic-packet → firewall or service activation) – T1205 v1.0
AN1448 WindowsA remote host sends a short sequence of failed connection attempts (RST/ICMP unreachable) to a set of closed ports. Within a brief window the endpoint (a) adds/enables a firewall rule or (b) a sniffer-backed process begins listening or opens a new socket, after which a successful connection occurs. Also detects Wake-on-LAN magic packets seen on local segment.WinEventLog:Microsoft-Windows-Windows Firewall With Advanced Security/Firewall
EventCode=2004, 2005, 2006→ DC0078 Network Traffic FlowTunable:TimeWindowKnockPortSequenceMinLenSuspiciousProcessesAllowedFirewallChangersWoLAllowedWindowsAN1449 LinuxClosed-port knock sequence from a remote IP followed by on-host firewall change (iptables/nftables) or daemon starts listening (socket open) and a successful TCP/UDP connect. Optional detection of libpcap/raw-socket sniffers spawning to watch for secret values.auditd:SYSCALLexecve: Commands altering firewall or enabling listeners (iptables, nft, ufw, firewall-cmd, systemctl start *ssh*/*telnet*, ip route add, tcpdump, tshark)→ DC0032 Process Creationauditd:SYSCALLsocket/bind: Process binds to a new local port shortly after knock→ DC0082 Network Connection CreationNSM:FlowKnock pattern: multiple REJ/S0 to distinct closed ports then successful connection to service_port→ DC0078 Network Traffic FlowNSM:FlowPackets with unusual flags or payloads outside established flows (e.g., WoL magic FF×6 + 16×MAC)→ DC0085 Network Traffic ContentTunable:ServicePortKnockResetRatioProcessAllowListAN1450 macOSRemote knock sequence followed by PF/socketfilterfw rule update or a background process listening on a new port; then a successful TCP session. Also flags WoL magic packets on local segment.macos:unifiedlogexec: Execution of /sbin/pfctl, /usr/libexec/ApplicationFirewall/socketfilterfw, ifconfig, tcpdump, npcap/libpcap consumers→ DC0032 Process Creationmacos:unifiedlogFirewall rule enable/disable or listen socket changes→ DC0078 Network Traffic FlowTunable:PFAnchorPathsDeveloperModeAN1451 Network DevicesCrafted ‘synful knock’ patterns toward routers/switches (same src hits interface/broadcast/network address on same port in short order) followed by ACL/telnet/SSH enablement or module change. Detect device image/ACL updates then a new mgmt session.networkdevice:syslogConfig/ACL/line vty changes, service enable (telnet/ssh/http(s)), module reloads→ DC0078 Network Traffic FlowNSM:FlowPort-knock pattern from one src to device unicast,broadcast,network addresses on same port within TimeWindowKnock→ DC0082 Network Connection CreationTunable:MgmtPortSetDeviceRole
Sigma rules · SigmaHQ da9bb07d64, tag attack.t1205
No Sigma rule carries this tag. MITRE publishes a detection strategy above, so the behaviour is specified; what is missing is public detection content.