Performing dynamic analysis in a sandbox

Performing Dynamic Analysis in a Sandbox

When to Use

• Static analysis is blocked by packing/obfuscation and you need to observe runtime behavior.
• You want a behavioral picture: spawned processes, dropped files, registry edits, and C2.
• You are confirming capabilities hypothesized from static analysis.

Do not use dynamic analysis as the only method — evasive samples may sleep, detect the sandbox, or require arguments. Pair it with static/RE work.

Prerequisites

• An isolated lab with a victim VM and simulated internet (see the lab-setup skill).
• A sandbox stack (CAPE/Cuckoo) or manual instrumentation: Process Monitor, Process Explorer, Regshot, and a packet capture on the services guest.
• A clean base snapshot to revert to.

Safety & Handling

• Detonate only inside the isolated victim VM; revert the snapshot after each run.
• Route all network through the simulated-internet guest; never allow live egress.
• Defang any captured URLs/IPs before they leave the lab.

Workflow

Step 1: Prepare instrumentation

Start Process Monitor (filtered to the target), Regshot baseline, and packet capture on the services guest. Snapshot the victim as clean.

Step 2: Detonate with the right context

Many samples need a parent (Office, rundll32), an export (rundll32 dll,Export), or arguments. Match the original delivery context or the sample stalls.

Step 3: Observe for the full behavior window

Watch process creation, file drops, registry Run keys/services, scheduled tasks, and network beacons. Give it several minutes; some samples sleep first.

Step 4: Summarize the report

Feed the sandbox JSON (or your collected logs) to the summarizer to group events into capabilities and IOCs:

python scripts/analyst.py summarize report.json

Step 5: Diff the system state

Compare Regshot/file baselines pre- and post-run to capture persistence and dropped artifacts.

Validation

• The observed process tree and network match the static-analysis hypothesis.
• Persistence mechanisms found dynamically are confirmed in registry/task artifacts.
• Re-running from the clean snapshot reproduces the core behavior.

Pitfalls

• Detonating without the required parent/args, so the sample exits early ("sandbox evasion" that is really a context problem).
• Too-short observation windows that miss sleeping or staged payloads.
• Trusting a single sandbox verdict; tune and corroborate.
• Allowing real network egress and contaminating live infrastructure.

References

• See references/api-reference.md for the report summarizer.
• CAPE Sandbox and Process Monitor (linked in frontmatter).