Obfuscated Files or Information: Compile After Delivery T1027.004
Tactic: Stealth
Adversaries may attempt to make payloads difficult to discover and analyze by delivering files to victims as uncompiled code. Text-based source code files may subvert analysis and scrutiny from protections targeting executables/binaries. These payloads will need to be compiled before execution; typically via native utilities such as ilasm.exe, csc.exe, or GCC/MinGW.
Events covered
3 catalog events are tagged with this technique by at least one rule.
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 1 | Process creation |
| Sysmon | Event ID 11 | FileCreate |
| Security-Auditing | Event ID 4688 | A new process has been created. |
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 (14 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 (155 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 (13 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 6 rules
- Csc.EXE Execution Form Potentially Suspicious Parent
- Dynamic .NET Compilation Via Csc.EXE
- Dynamic .NET Compilation Via Csc.EXE - Hunting
- Dynamic CSharp Compile Artefact
- Potential Application Whitelisting Bypass via Dnx.EXE
- Visual Basic Command Line Compiler Usage
Elastic 3 rules
- GenAI Process Compiling or Generating Executables
- Microsoft Build Engine Started an Unusual Process
- Suspicious .NET Code Compilation