Sub-technique of T1205 Traffic Signaling.View on attack.mitre.org
Adversaries may attach filters to a network socket to monitor then activate backdoors used for persistence or command and control. With elevated permissions, adversaries can use features such as the `libpcap` library to open sockets and install filters to allow or disallow certain types of data to come through the socket. The filter may apply to all traffic passing through the specified network interface (or every interface if not specified). When the network interface receives a packet matching the filter criteria, additional actions can be triggered on the host, such as activation of a reverse shell.
To establish a connection, an adversary sends a crafted packet to the targeted host that matches the installed filter criteria. Adversaries have used these socket filters to trigger the installation of implants, conduct ping backs, and to invoke command shells. Communication with these socket filters may also be used in conjunction with Protocol Tunneling.
Filters can be installed on any Unix-like platform with `libpcap` installed or on Windows hosts using `Winpcap`. Adversaries may use either `libpcap` with `pcap_setfilter` or the standard library function `setsockopt` with `SO_ATTACH_FILTER` options. Since the socket connection is not active until the packet is received, this behavior may be difficult to detect due to the lack of activity on a host, low CPU overhead, and limited visibility into raw socket usage.
Rules on DetectionCode tagged with T1205.002.
None recorded.
None recorded.
| Used by | Procedure example |
|---|---|
| MalwareBPFDoor | BPFDoor uses BPF bytecode to attach a filter to a network socket to view ICMP, UDP, or TCP packets coming through ports 22 (ssh), 80 (http), and 443 (https). When BPFDoor finds a packet containing its “magic” bytes, it parses out two fields and forks itself. The parent process continues to monitor filtered traffic while the child process executes the instructions from the parsed fields. |
| MalwareCASTLETAP | CASTLETAP can listen for a specialized ICMP packet for activation on compromised network devices. |
| MalwarePenquin | Penquin installs a `TCP` and `UDP` filter on the `eth0` interface. |
| MalwarePITSTOP | PITSTOP can listen and evaluate incoming commands on the domain socket, created by PITHOOK malware, located at `/data/runtime/cockpit/wd.fd` for a predefined magic byte sequence. PITSTOP can then duplicate the socket for further communication over TLS. |
Data from MITRE ATT&CK® (Enterprise). ATT&CK® is a registered trademark of The MITRE Corporation.
