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kosermuy-maker

link-checkup

by kosermuy-maker
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Link Checkup · 可疑链接体检

Check a suspicious link — without opening it. Paste a URL from a text, email, chat or QR code and get a 0–100 risk score, per-check findings and a one-sentence verdict in English and 简体中文. The page is never rendered, no JavaScript runs and nothing is downloaded.

Built for the Kiro University Challenge 2026 final exam. Uses only free, keyless data sources.

Lookalike detection

The problem

I get links I don't trust all the time — "your parcel is on hold", "verify your account", a friend's hacked account sending "is this you in the video?". My habit is to forward them to an assistant to screen them before anyone clicks, so my phone, laptop and accounts are never exposed. Opening a link "just to see" is exactly what the attacker wants: it can fingerprint the device, trigger a download, or show a pixel-perfect fake login.

Link Checkup turns that screening into a repeatable tool. It answers who really owns this link, how old is it, where does it really go, and is it already known to be bad — using only DNS, a TLS handshake and HTTP headers. It works as a web page, a CLI, an MCP server, and a Kiro custom agent (link-triage) that screens links on my behalf.

Related MCP server: Malicious Scanner MCP Server

What it checks

Check

How (free, no API key)

Example signals

Public blocklists

URLhaus online-URL text feed + Phishing Army domain list, cached 1 h, string-matched only

listed URL / domain → critical (score ≥ 90)

Lookalike / typosquat

Local: confusable-character skeletons, Damerau–Levenshtein, combosquat, brand-in-subdomain, mixed scripts / punycode vs. 49 brands

paypa1, Cyrillic аpple, paypal.com.account-verify.example

Domain age & registrar

RDAP (rdap.org bootstrap)

registered < 30 days, registry hold

Redirect chain

HEAD (or zero-byte ranged GET), ≤ 8 hops, 6 s timeouts, SSRF-guarded

cross-site hops, https→http, javascript: targets, loops

TLS certificate

Bare TLS handshake (SNI), no HTTP request

invalid / expired / mismatched cert, issued < 7 days

DNS

DNS-over-HTTPS (Cloudflare → Google fallback)

NXDOMAIN, resolves to private IPs

URL structure

Local parsing

raw IP, user@host trick, odd port, deep subdomains, abused TLDs

Safety design (see network-safety.md): every connection to a user-supplied host goes through src/net/safeRequest.ts: all resolved IPs must be public unicast (loopback, RFC1918, link-local, CGNAT, ULA, IPv4-mapped/NAT64/6to4 forms are refused), the vetted IP is pinned to defeat DNS rebinding, only ports 80/443 are contacted, response bodies are never read. Unknown results (timeouts, errors) add 0 points — unknown ≠ dangerous.

Scoring (src/scoring.ts): sum of finding points clamped to 0–100; any critical finding forces ≥ 90; levels: low < 25 ≤ medium < 60 ≤ high. These invariants are enforced by property-based tests.

Run it

Requires Node.js ≥ 20.

git clone https://github.com/kosermuy-maker/link-checkup && cd link-checkup
npm install
npm start                      # → http://127.0.0.1:8787  (English / 中文 toggle)

CLI and MCP:

npm run check -- "hxxp://paypa1[.]example/login"         # defanged input is fine
npm run check -- https://example.com --lang zh
npm run check -- https://example.com --json
npm run check -- paypa1.example --offline                # local checks only, no network
npm run mcp                                              # stdio MCP server (check_url, check_lookalike)
npm run mcp:smoke                                        # spawns the MCP server and calls both tools
npm test && npm run typecheck                            # 77 unit + property-based tests

API: POST /api/check with {"url": "..."} → JSON report (8 KB body limit, 30 checks/min per client).

Demo safely. Use benign domains (example.com, github.com) and synthetic lookalikes on reserved TLDs (paypa1.example, secure-paypal-login.test). Never paste real phishing links into demos or tests.

Deploying is optional (it's a plain Node server; any free Node host works). It is designed to run locally.

Hooks not firing or MCP panel empty in Kiro? See docs/kiro-troubleshooting.md: trust the workspace, then Reload Window.

How each Kiro lesson is used

#

Lesson

Where

How it is used

1

Spec-driven development

.kiro/specs/link-checkup/requirements.md, design.md, tasks.md

11 requirements with EARS acceptance criteria (e.g. "WHEN a Target hostname resolves to any address that is not a Public address THE System SHALL refuse to connect"), a design with architecture + sequence diagrams, and a task plan whose items reference requirement numbers. Git history follows the task list.

2

Steering

.kiro/steering/ product.md, tech.md, structure.md (always), network-safety.md (fileMatch on src/net/**, src/checks/**), adding-checks.md (auto)

Encodes the product promise ("never open the page"), the stack and hard rules (all target traffic via safeRequest, bilingual findings, pure scoring), the folder map and the point scale, with correct/incorrect code examples.

3

Hooks

.kiro/hooks/

run-tests-on-save.json (PostFileSave → npm test), verify-after-spec-task.json (PostTaskExec → typecheck + tests after each spec task), update-docs-on-new-check.json (PostFileCreate in src/checks/ → agent prompt to wire up i18n, tests, README, steering), i18n-parity-on-save.json (PostFileSave → scripts/hooks/check-i18n.mjs), guard-suspicious-fetch.json (PreToolUse → scripts/hooks/guard-shell.mjs blocks curl/wget/browsers on non-allowlisted hosts — the agent must use Link Checkup instead).

4

Property-based testing

design.md → Correctness Properties 1–10; optional * PBT tasks in tasks.md; test/*.property.test.ts + property cases in normalize.test.ts, redirects.test.ts (fast-check)

Score bounded / monotonic / critical ≥ 90 / level partition; no false positives on any official brand subdomain; every single-character homoglyph substitution of a brand is caught; edit-distance metric laws; every private IPv4/IPv6 (incl. IPv4-mapped) is blocked; URL normalisation idempotent; redirect following terminates for any random redirect graph. Each test is tagged with its property and the requirement it validates.

5

Powers

powers/link-checkup/ (plugin.json, mcp.json, skills/triage-link, skills/phishing-red-flags)

The checker packaged as an Agent-Plugins power: keywords like "phishing", "suspicious link", "可疑链接" activate it; its MCP server is launched with npx straight from this GitHub repo; skills carry the triage procedure and a finding glossary. Import via Powers → Add Custom Power → Import power from GitHub/folder.

6

MCP

src/mcp/server.ts, .kiro/settings/mcp.json, test/mcp.test.ts

Project MCP server exposing check_url (full checkup, EN/中文 summary + structured output) and check_lookalike (offline). Registered as workspace MCP server link-checkup (auto-approved tools); also declared inside the link-triage agent and the power's mcp.json.

7

Custom agents

.kiro/agents/link-triage.json + prompts/link-triage.md; .kiro/agents/check-builder.md

link-triage: read-only agent that uses only the workspace link-checkup MCP server (tools: ["@link-checkup"], includeMcpJson: false keeps other servers out) and pre-approves only check_url / check_lookalike; web, shell and write are excluded and denied by permissions, so it cannot open a link — it answers with a bilingual verdict + one concrete action, guided by its prompt file and the triage-link skill. check-builder (Markdown format): developer agent limited to npm/git commands and writes under src/, test/, docs, preloaded with steering + design.

★

Bonus: Package a Kiro power

powers/link-checkup/

Validated against the Agent Plugins 1.0.0 plugin.json / mcp.json schemas.

Project layout

src/            engine (checks, net guard, scoring, explain), server, CLI, MCP server
public/         static bilingual UI (no build step)
test/           vitest unit tests + fast-check property tests
powers/         Kiro power package
.kiro/          specs, steering, hooks, settings/mcp.json, agents, skills
scripts/        hook helpers, MCP smoke test, screenshot script

Screenshots

Home

Subdomain trick (中文)

Benign redirect

Lookalike

Screenshots were produced headlessly with Playwright (scripts/screenshots.mjs) against the local server.

Limitations

  • A low score is not a guarantee; brand-new attacks may not be on blocklists yet.

  • The brand list is curated (49 brands) and typosquat detection can flag legitimate look-alike names (e.g. chaser.com) — findings explain why, and the score is only a guide.

  • RDAP coverage varies by TLD (some ccTLDs don't publish RDAP); that check then reports "not checked".

  • Phishing Army's list is CC BY-NC 4.0: it is downloaded at runtime, not redistributed.

License

MIT

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