Attack Ent T1539 Steal Web Session Cookie

MITRE ATT&CK T1539: Steal Web Session Cookie

When to use this skill

Use this skill when the task involves T1539, Steal Web Session Cookie, 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 technique.

Technique context

• ATT&CK domain: enterprise
• ATT&CK ID: T1539
• Technique name: Steal Web Session Cookie
• Type: technique
• ATT&CK URL: https://attack.mitre.org/techniques/T1539
• Tactics: credential-access
• Platforms: Linux, macOS, Office Suite, SaaS, Windows
• Required permissions: Not specified
• Effective permissions: Not specified
• Defenses bypassed: Not specified

ATT&CK description

An adversary may steal web application or service session cookies and use them to gain access to web applications or Internet services as an authenticated user without needing credentials. Web applications and services often use session cookies as an authentication token after a user has authenticated to a website.

Cookies are often valid for an extended period of time, even if the web application is not actively used. Cookies can be found on disk, in the process memory of the browser, and in network traffic to remote systems. Additionally, other applications on the targets machine might store sensitive authentication cookies in memory (e.g. apps which authenticate to cloud services). Session cookies can be used to bypasses some multi-factor authentication protocols.(Citation: Pass The Cookie)

There are several examples of malware targeting cookies from web browsers on the local system.(Citation: Kaspersky TajMahal April 2019)(Citation: Unit 42 Mac Crypto Cookies January 2019) Adversaries may also steal cookies by injecting malicious JavaScript content into websites or relying on User Execution by tricking victims into running malicious JavaScript in their browser.(Citation: Talos Roblox Scam 2023)(Citation: Krebs Discord Bookmarks 2023)

There are also open source frameworks such as Evilginx2 and Muraena that can gather session cookies through a malicious proxy (e.g., Adversary-in-the-Middle) that can be set up by an adversary and used in phishing campaigns.(Citation: Github evilginx2)(Citation: GitHub Mauraena)

After an adversary acquires a valid cookie, they can then perform a Web Session Cookie technique to login to the corresponding web application.

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

• Audit
• Multi-factor Authentication
• Restrict Web-Based Content
• Software Configuration
• Update Software
• User Training

Known threat context

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

• APT42 (intrusion-set)
• BLUELIGHT (malware)
• Chaes (malware)
• CookieMiner (malware)
• DarkGate (malware)
• EVILNUM (malware)
• Evilnum (intrusion-set)
• GlassWorm (malware)
• Grandoreiro (malware)
• Kimsuky (intrusion-set)
• LODEINFO (malware)
• Lotus Blossom (intrusion-set)
• LuminousMoth (intrusion-set)
• Lumma Stealer (malware)
• MgBot (malware)
• QakBot (malware)
• Raccoon Stealer (malware)
• RedLine Stealer (malware)
• Sandworm Team (intrusion-set)
• Scattered Spider (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

• Microsoft Threat Intelligence Center (MSTIC)
• Johann Rehberger
• Menachem Goldstein
• Don Le, Stifel Financial