Pre-ring scam shield: why your UK business phone should flag scam calls before it rings

UK businesses got 33 million unsolicited / scam calls in 2025 according to Ofcom. Most spam-filter products run after the call rings — which means your receptionist or sales agent has already been interrupted. We do it differently.

How the Silux Call scam shield works

1. Inbound call hits the dialplan macro
2. silux-scam-shield
3. .
4. A loopback call goes to the backend within 0.2 s with the caller-ID and called DDI.
5. The shield evaluates your own rules, the Silux block list and fixed checks (anonymous CLI, impossible or all-zeros numbers, spoofed numbers that the real organisation never dials out from).
6. Depending on your policy the call is labelled "Likely scam" on the handset or rejected
7. before
8. the phone rings.

What gets blocked

• Spoofed HMRC / DVLA "tax owed" scams (rotating UK 0800 ranges).
• Royal Mail / DPD / Evri parcel-fee scams (overseas CLI, UK destination).
• Microsoft / BT "your account is compromised" wardialers.
• Anonymous / "withheld" calls if your tenant policy includes them.

Tenant control

Add your own block patterns at Dashboard → Scam Shield. Patterns support glob (+44800111111*), and actions are block / voicemail / challenge / allow. The hit log shows the 100 most recent screened calls with the rule that fired.

Which plans include it?

The scam & spam shield is included on Growth and above, and available as a £3.95/month add-on on any paid plan. It is rule-based, not AI. See our comparison for how other providers handle scam calls.