T1205.002 Socket Filters Mappings

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.(Citation: haking9 libpcap network sniffing) 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.(Citation: exatrack bpf filters passive backdoors)(Citation: Leonardo Turla Penquin May 2020)

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.

View in MITRE ATT&CK®

VERIS Mappings

Capability ID Capability Description Mapping Type ATT&CK ID ATT&CK Name Notes
action.hacking.variety.Evade Defenses Modification of the action (rather than the system, as in 'Disable controls') to avoid detection. related-to T1205.002 Traffic Signaling: Socket Filters

AWS Mappings

Capability ID Capability Description Mapping Type ATT&CK ID ATT&CK Name Notes
aws_network_firewall AWS Network Firewall technique_scores T1205.002 Socket Filters
Comments
AWS Network Firewall can be used to block traffic to unused ports from reaching hosts on the network which may help protect against traffic signaling from external systems. This mapping is given a score of partial because the AWS Network Firewall does not do anything to protect against traffic signaling among hosts within the network and behind the firewall.
References