Attack Ent T1505 003 Web Shell

MITRE ATT&CK T1505.003: Web Shell

When to use this skill

Use this skill when the task involves T1505.003, Web Shell, enterprise ATT&CK, TTP mapping, detection engineering, hunting, incident-response enrichment, control validation, or authorized adversary-emulation planning. Treat it as a defensive analysis aid: keep outputs focused on understanding, detecting, mitigating, and safely validating this ATT&CK sub-technique.

Technique context

• ATT&CK domain: enterprise
• ATT&CK ID: T1505.003
• Technique name: Web Shell
• Type: sub-technique
• ATT&CK URL: https://attack.mitre.org/techniques/T1505/003
• Tactics: persistence
• Platforms: Linux, macOS, Network Devices, Windows
• Required permissions: Not specified
• Effective permissions: Not specified
• Defenses bypassed: Not specified

ATT&CK description

Adversaries may backdoor web servers with web shells to establish persistent access to systems. A Web shell is a Web script that is placed on an openly accessible Web server to allow an adversary to access the Web server as a gateway into a network. A Web shell may provide a set of functions to execute or a command-line interface on the system that hosts the Web server.(Citation: volexity_0day_sophos_FW)

In addition to a server-side script, a Web shell may have a client interface program that is used to talk to the Web server (e.g. China Chopper Web shell client).(Citation: Lee 2013)

Agent workflow

1. Clarify scope: identify the system, asset class, log sources, cloud or endpoint platform, and whether the user wants triage, detection, coverage assessment, or safe emulation planning.
2. Load bundled resources as needed: use references/technique-profile.json for structured metadata, references/detection-and-mitigation.md for triage and telemetry guidance, references/known-threat-context.md for ATT&CK relationship context, and templates/ for repeatable outputs.
3. Map observations to ATT&CK: compare the user's evidence to the ATT&CK description, tactics, platforms, and known procedure patterns before asserting a match.
4. Produce defensive outputs: prioritize hypotheses, telemetry requirements, detection logic ideas, validation steps, containment guidance, and mitigations.
5. Preserve uncertainty: distinguish confirmed evidence, plausible indicators, assumptions, and gaps. Recommend what to collect next.
6. Stay safe: do not provide malware, credential theft, persistence, evasion, destructive automation, or unauthorized exploitation instructions. For adversary emulation, keep steps bounded to approved lab or control-validation contexts and omit operational abuse details.

Bundled resources

• references/technique-profile.json: machine-readable ATT&CK metadata for this technique.
• references/detection-and-mitigation.md: detection notes, telemetry checklist, triage questions, mitigation candidates, and false-positive considerations.
• references/known-threat-context.md: ATT&CK relationship context with attribution cautions.
• templates/detection-brief.md: detection engineering brief template.
• templates/hunt-plan.md: threat hunt plan template.
• templates/incident-response-note.md: incident response note template.
• templates/coverage-assessment.md: ATT&CK coverage assessment template.
• scripts/render_brief.py: local helper that renders a Markdown defensive brief from technique-profile.json.
• assets/output-schema.json: JSON schema for structured technique analysis outputs.

To generate a quick brief, run python scripts/render_brief.py --output brief.md from inside this skill directory, or adapt the templates directly.

Detection guidance

No ATT&CK detection guidance was present in the source STIX object.

Useful telemetry and data sources

• Not specified in the STIX object.

Mitigations to consider

• Disable or Remove Feature or Program
• User Account Management

Known threat context

Use these examples only as contextual leads, not as proof that an observed event is this technique:

• 2022 Ukraine Electric Power Attack (campaign)
• APT28 (intrusion-set)
• APT29 (intrusion-set)
• APT32 (intrusion-set)
• APT38 (intrusion-set)
• APT39 (intrusion-set)
• APT41 DUST (campaign)
• APT5 (intrusion-set)
• ASPXSpy (malware)
• Agrius (intrusion-set)
• BUSHWALK (malware)
• BackdoorDiplomacy (intrusion-set)
• BlackByte (intrusion-set)
• C0017 (campaign)
• C0032 (campaign)
• CURIUM (intrusion-set)
• China Chopper (malware)
• Cutting Edge (campaign)
• Deep Panda (intrusion-set)
• Dragonfly (intrusion-set)

Recommended output pattern

When responding with this skill, structure the answer as:

• Assessment: whether the evidence supports this ATT&CK mapping and why.
• Evidence: specific indicators, logs, behaviors, and assumptions.
• Detection: telemetry sources, analytic logic, and tuning considerations.
• Response: containment, eradication, recovery, and validation actions.
• Coverage gaps: missing logs, sensors, controls, or environmental details.
• References: include the ATT&CK URL and any user-provided evidence references.

ATT&CK contributors

• Arnim Rupp, Deutsche Lufthansa AG