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
16 catalog events are tagged with this technique by at least one rule.
Authoring guide
Patterns shared across the 14 rules above: which fields they filter on, what specific values they look for, and what they exclude. The catalog normalizes field names 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 (18 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.
Top indicator values (40 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. Click a value to expand the rules under this technique that use it.
Exclusions (9 distinct)
Field/operator/value combinations excluded by rules under this technique (top-level not() clauses), sorted by how many rules exclude each. These are the false-positive paths the community has learned to filter out. A new rule that ignores the high-count entries here will likely fire on the same noisy paths. Click a value to expand the rules under this technique that exclude it.
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 4 rules
- Network Communication Initiated To Portmap.IO Domain
- Shai-Hulud NPM Package Malicious Exfiltration via Curl
- Tunneling Tool Execution
- Vice Society directory crawling script for data exfiltration (via ps_script)
Splunk 6 rules
- Potential Telegram API Request Via CommandLine
- Powershell ICMP Data Exfiltration (PowerShell)
- Script Connected to External Destination - Windows (Sysmon)
- Script Connected to External Destination - Windows (Windows Event Log)
- Windows Exfiltration Over C2 Via Invoke RestMethod
- Windows Exfiltration Over C2 Via Powershell UploadString