Fraud and KYC

Line-type detection at onboarding

Telebase returns the line type for any phone number, distinguishing mobile, landline, fixed VoIP and non-fixed VoIP in a single API call. Non-fixed VoIP numbers, the kind bought for a few pounds from a web app with no identity check, are the highest-risk category at consumer onboarding. Identifying them before an application proceeds costs 0.03 USD per query, requires no action from the customer, and takes milliseconds.

Why line type is the right first check at onboarding

Most fraud prevention starts with the person. Line-type detection starts with the number, and it surfaces a signal that identity data alone cannot: whether the phone number is the kind of number a legitimate customer in your target market would actually have.

A consumer signing up for a neobank, lending product or crypto exchange in the UK is almost certainly presenting a mobile number. If the number is non-fixed VoIP, that is already worth flagging before any document check begins. Non-fixed VoIP numbers require no identity verification to obtain, can be created in seconds and are discarded after use. Fraud rings use them at scale.

Line-type detection does not replace document verification or database screening. It is a fast, low-cost filter at the earliest stage of the funnel, before you have spent any meaningful time or money on the application.

Line types Telebase returns

The distinction between fixedVoip and nonFixedVoip matters. A fixed VoIP line tied to a business address carries different risk from a non-fixed VoIP number created anonymously in thirty seconds. Treating them identically leads to either over-blocking legitimate business customers or under-flagging genuine fraud risk.

How to use line-type detection in an onboarding flow

The most practical integration point is immediately after the customer submits their phone number, before any OTP is sent. A non-fixed VoIP number cannot receive a delivery guarantee from most SMS providers anyway, so sending an OTP to one is wasted cost on top of the fraud risk.

Suggested logic:

• nonFixedVoip: decline the number and ask the customer to provide a mobile or landline. Most legitimate customers will not object.
• fixedVoip: route to manual review or apply a higher friction path rather than a hard block, since some legitimate business customers use these.
• tollFree or voicemail: decline. These are not plausible consumer contact numbers.
• mobile or landline and active: false: flag for review. An inactive number is worth understanding before the application proceeds.

Example call

curl -s 'https://telebase.fatcatremote.com/api/lookup?phone=%2B447700900000' \
  -H 'Authorization: Bearer tb_live_xxxxxxxxxxxxxxxxxxxxxxxx'

{
  "phoneNumber": "+447700900000",
  "active": true,
  "carrier": "EE",
  "country": "GB",
  "numberType": "mobile",    // mobile | landline | fixedVoip | nonFixedVoip | tollFree | voicemail
  "simSwap": "UNKNOWN",     // launching for GB, DE, NL and FR
  "simSwapAt": null,
  "_meta": { "activeSource": "LINE_STATUS" }
}

Phone numbers must be E.164 with the leading + URL-encoded as %2B. New accounts receive a USD 5.00 starting balance.