Attack Ent T1598 003 Spearphishing Link

MITRE ATT&CK T1598.003: Spearphishing Link

When to use this skill

Use this skill when the task involves T1598.003, Spearphishing Link, 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: T1598.003
• Technique name: Spearphishing Link
• Type: sub-technique
• ATT&CK URL: https://attack.mitre.org/techniques/T1598/003
• Tactics: reconnaissance
• Platforms: PRE
• Required permissions: Not specified
• Effective permissions: Not specified
• Defenses bypassed: Not specified

ATT&CK description

Adversaries may send spearphishing messages with a malicious link to elicit sensitive information that can be used during targeting. Spearphishing for information is an attempt to trick targets into divulging information, frequently credentials or other actionable information. Spearphishing for information frequently involves social engineering techniques, such as posing as a source with a reason to collect information (ex: Establish Accounts or Compromise Accounts) and/or sending multiple, seemingly urgent messages.

All forms of spearphishing are electronically delivered social engineering targeted at a specific individual, company, or industry. In this scenario, the malicious emails contain links generally accompanied by social engineering text to coax the user to actively click or copy and paste a URL into a browser.(Citation: TrendMictro Phishing)(Citation: PCMag FakeLogin) The given website may be a clone of a legitimate site (such as an online or corporate login portal) or may closely resemble a legitimate site in appearance and have a URL containing elements from the real site. URLs may also be obfuscated by taking advantage of quirks in the URL schema, such as the acceptance of integer- or hexadecimal-based hostname formats and the automatic discarding of text before an “@” symbol: for example, hxxp://google.com@1157586937.(Citation: Mandiant URL Obfuscation 2023)

Adversaries may also embed “tracking pixels,” "web bugs," or "web beacons" within phishing messages to verify the receipt of an email, while also potentially profiling and tracking victim information such as IP address.(Citation: NIST Web Bug)(Citation: Ryte Wiki) These mechanisms often appear as small images (typically one pixel in size) or otherwise obfuscated objects and are typically delivered as HTML code containing a link to a remote server.(Citation: Ryte Wiki)(Citation: IAPP)

Adversaries may also be able to spoof a complete website using what is known as a "browser-in-the-browser" (BitB) attack. By generating a fake browser popup window with an HTML-based address bar that appears to contain a legitimate URL (such as an authentication portal), they may be able to prompt users to enter their credentials while bypassing typical URL verification methods.(Citation: ZScaler BitB 2020)(Citation: Mr. D0x BitB 2022)

Adversaries can use phishing kits such as EvilProxy and Evilginx2 to perform adversary-in-the-middle phishing by proxying the connection between the victim and the legitimate website. On a successful login, the victim is redirected to the legitimate website, while the adversary captures their session cookie (i.e., Steal Web Session Cookie) in addition to their username and password. This may enable the adversary to then bypass MFA via Web Session Cookie.(Citation: Proofpoint Human Factor)

Adversaries may also send a malicious link in the form of Quick Response (QR) Codes (also known as “quishing”). These links may direct a victim to a credential phishing page.(Citation: QR-campaign-energy-firm) By using a QR code, the URL may not be exposed in the email and may thus go undetected by most automated email security scans.(Citation: qr-phish-agriculture) These QR codes may be scanned by or delivered directly to a user’s mobile device (i.e., Phishing), which may be less secure in several relevant ways.(Citation: qr-phish-agriculture) For example, mobile users may not be able to notice minor differences between genuine and credential harvesting websites due to mobile’s smaller form factor.

From the fake website, information is gathered in web forms and sent to the adversary. Adversaries may also use information from previous reconnaissance efforts (ex: Search Open Websites/Domains or Search Victim-Owned Websites) to craft persuasive and believable lures.

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

• Software Configuration
• User Training

Known threat context

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

• AADInternals (tool)
• APT28 (intrusion-set)
• APT32 (intrusion-set)
• CURIUM (intrusion-set)
• Dragonfly (intrusion-set)
• Kimsuky (intrusion-set)
• Magic Hound (intrusion-set)
• Moonstone Sleet (intrusion-set)
• Mustang Panda (intrusion-set)
• Patchwork (intrusion-set)
• SMOKEDHAM (malware)
• Sandworm Team (intrusion-set)
• Scattered Spider (intrusion-set)
• Sidewinder (intrusion-set)
• Silent Librarian (intrusion-set)
• Star Blizzard (intrusion-set)
• ZIRCONIUM (intrusion-set)
• evilginx2 (tool)

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

• Philip Winther
• Sebastian Salla, McAfee
• Menachem Goldstein
• Robert Simmons, @MalwareUtkonos
• Elpidoforos Maragkos, @emaragkos
• Joas Antonio dos Santos, @C0d3Cr4zy
• Austin Herrin
• Obsidian Security
• Sam Seabrook, Duke Energy