ATT&CK coverage › Technique

Exfiltration Over C2 Channel T1041

Adversaries may steal data by exfiltrating it over an existing command and control channel. Stolen data is encoded into the normal communications channel using the same protocol as command and control communications.

Events covered

11 catalog events are tagged with this technique by at least one rule.

ProviderEvent IDTitle
Sysmon3Network connection
Security-Auditing4688A new process has been created.
Security-Auditing5152The Windows Filtering Platform blocked a packet.
Security-Auditing5154The Windows Filtering Platform has permitted an application or service to listen on a port for incoming connections.
Security-Auditing5155The Windows Filtering Platform has blocked an application or service from listening on a port for incoming connections.
Security-Auditing5156The Windows Filtering Platform has permitted a connection.
Security-Auditing5157The Windows Filtering Platform has blocked a connection.
Security-Auditing5158The Windows Filtering Platform has permitted a bind to a local port.
Security-Auditing5159The Windows Filtering Platform has blocked a bind to a local port.
Defender-DeviceEvents9007000Defender event (any)
PowerShell4104Creating Scriptblock text (MessageNumber of MessageTotal).

Authoring guide

Patterns shared across the 6 rules above: which fields they filter on, what specific values they look for, and what they exclude. Field names are normalized across vendors so Sigma's Image, Elastic's process.name, and Splunk's process_name collapse into one row. Each rule contributes at most once per row.

Fields filtered most (6 distinct)

The fields most rules look at when detecting this technique. The How column shows the operators authors use (eq, wildcard, regex_match, match) and how often each appears. Sample values are concrete examples to start from, not an exhaustive list.

FieldRulesHowSample values
ScriptBlockText2eq 2"* -Method *", "*Invoke-RestMethod *", "* -InFile *", "*Net.webclient*", "*.UploadString*"
EventID2eq 24104
dest_ip1is_not_null 1
user1is_not_null 1
DestinationHostname1ends_with 1.portmap.io
Initiated1eq 1true

Top indicator values (10 distinct)

Specific (field, operator, value) combinations the rules check for, ranked by how many rules under this technique use each one. The Corpus reach column counts how many rules across the entire catalog (any technique) check the same combination. High numbers point to widely-used indicators that are likely noisy on their own; combine them with another condition for useful signal. Blank means the combination is specific to rules under this technique.

FieldKindValueRules (here)Corpus reach
EventIDeq41042108
Initiatedeqtrue140
DestinationHostnameends_with.portmap.io1
ScriptBlockTexteq"* -Method *"1
ScriptBlockTexteq"*Invoke-RestMethod *"1
ScriptBlockTexteq"* -InFile *"1
ScriptBlockTexteq"* -Uri *"1
ScriptBlockTexteq"* Post *"1
ScriptBlockTexteq"*Net.webclient*"1
ScriptBlockTexteq"*.UploadString*"1

Rules under this technique

Every rule in the catalog tagged with this technique, grouped by vendor. Click a rule title for its full predicates, exclusions, and indicators.

Sigma 1 rule

Splunk 2 rules

Kusto Query Language 3 rules