scam-pattern-catalog

name	Scam Pattern Catalog
description	This skill should be used when performing scam detection to recognize Berlin rental fraud patterns. Reference before classifying any listing as ok, review, or block.

Hard Block Signals (weight 0.8+)

These are near-certain fraud. Auto-block without LLM confirmation.

• Western Union / MoneyGram payment requests in any form
• "Send deposit before viewing" — Kaution vor Besichtigung überweisen
• Bitcoin / crypto / Kryptowährung payment requests
• Landlord-abroad framing — "Ich bin im Ausland / im Urlaub und schicke die Schlüssel per Post"
• Keys by mail — offering to mail keys without an in-person meeting

Strong Signals (weight 0.4–0.6)

Require at least one of these + another signal to block. Single occurrence = review.

• WhatsApp-only contact — "Bitte nur per WhatsApp / nur Whatsapp" (note: phone number in description is normal on Kleinanzeigen — this signal is about exclusivity)
• Price >50% below Mietspiegel for size + district (see berlin-context skill)
• Airbnb framing — "flexible stays", nightly rates mentioned
• Google Translate artifacts — grammatically broken formal German (e.g., "Ich brauche ehrliche und sorgfältige Mieter")
• Multiple portals, same description, different photos — coordinated scam operation

Moderate Signals (weight 0.2–0.4)

These alone don't classify a listing. They raise the threshold for ok classification.

• Price 35–50% below Mietspiegel
• Ablöse >€2,000 for used furniture
• Kaution >3× cold rent (illegal, §551 BGB)
• Landlord name is a generic English name ("John Smith", "David Williams", "Mary Johnson")
• No address given, only "Berlin" with no district — common for legit listings but lowers confidence
• Listing is very old (>90 days) at an unusually low price

Swap Signals (filtered, not scam)

Not scam, but filtered by deal_breakers config.

• Keywords: Tausch, Wohnungstausch, biete gegen, suche im Tausch
• Listing requires a counter-offer property

Portal-Specific Notes

Kleinanzeigen:

• Phone numbers in description: normal for private landlords — weight only 0.15 (not 0.30)
• "Nur Selbstnutzer": legitimate signal, ignore
• Very low-priced listings (€300–500) for large flats in central districts: almost always scam

ImmoScout24:

• Premium-contact wall on private listings: unusual, flag for review
• Agency listings with "Provision frei" but then mentioning fees elsewhere: flag

Scoring Logic

total_score = sum of triggered weights, capped at 1.0
block  if score >= 0.85
review if score >= 0.55
ok     if score <  0.55

LLM judgment is the last layer — invoke only when rule-based score is in the 0.40–0.84 range.