SMS Security: Why SPIDs Are Important

Close-up of phone screen to show sms security

There are plenty of ways you can boost your SMS security. Your phone carrier has its own SMS security methods, too. SPIDs are one of your phone carrier’s tools for monitoring business text messaging use. 

What Is an SPID?

A service profile identifier (SPID) is a number assigned to an integrated services digital network (ISDN) line by a telephone carrier. It indicates which services the ISDN device can access. 

In layman’s terms, the SPID tells your telephone carrier where to route SMS/MMS messages.

Most U.S. telephone companies use the generic SPID Format, which is a 14-digit number. Some telephone companies may also refer to the SPID as NNID (non-adjacent network identifier). The first 10 digits identify the telephone number, called the directory number (DN). The last four digits identify a particular ISDN device, in the case where multiple devices share the same directory number.

What Do SPIDs Have to Do with Business Text Messaging? 

Traditional phone numbers like landlines do not have a SPID identifier, which means that these numbers cannot send nor receive SMS/MMS. With a number that has an SPID, you can send, receive and reply to messages from customers and reply to their texts. With certain kinds of numbers, like a short code, you can text customers but not reply to them. Whether or not a business number has an SPID also determines the setup process for your business text messaging platform.

What Do SPIDs Have to Do with SMS Security? 

The different types of phone numbers are critical to SMS security. They empower your phone carrier to regulate and monitor business use of phone calls and texting. For example, if you have a VoIP or mobile business line, carriers can ensure that the business text messaging platform that you are transferring your SPID to is configured properly and legitimately before allowing you to text from your business number. Without SPID routing and setup, it would be more difficult for carriers to control business-to-customer communications. 

What Types of Business Numbers Are There?

There are many types of business numbers. Some have SPIDs and some do not. Whether or not they have SPIDs dictates the number’s capabilities—and how you can transfer SMS capabilities to your business text messaging platform. 

A business number might be a:

  • Landline. This is your basic, old-fashioned phone line, which relies on physical cables on the public switched telephone network (PSTN). This network includes traditional copper wires on the plain old telephone service (POTS). Landlines don’t have a SPID and can’t interact with online data. However, when you choose to text-enable this line, a provider (like Twilio) will create a SPID that allows you to route texts to your business text messaging inbox.
  • Voice over internet protocol (VoIP). This type of number allows you to call other numbers using the internet. Sometimes it has texting capabilities, too. Some carriers allow their numbers’ ISDN to be routed to another carrier, splitting off the text capabilities so that you can have customer messages arrive in your business text messaging platform. Other carriers explicitly do not allow the SPID to be separated from their native systems. 
  • Mobile business line. A mobile phone has a specific SPID that designates it as a mobile phone number (unique to each major consumer mobile carrier like Verizon, AT&T, Rogers, or Bell) . Most, if not all, of these carriers don’t allow their mobile phone SPIDs to be transferred to a business text messaging platform. This is a good thing, as it prevents bad actors from accessing the messaging capabilities of consumer mobile phone numbers.

Ultimately, carriers can use the SPID on your business line (if you have one) to carefully monitor any transference of service. It’s their way of making sure customers are being contacted by a reputable business through a reputable business text messaging service.  


Want to learn more about SMS security? Check out our SMS Compliance Checklist for 2021.

As Heymarket’s Senior Content Marketing Manager, Hailey Colwell creates texting resources that help brands make meaningful connections with their customers. Her background combines CRM software and journalism, including writing for American Public Media. When she's not editing, she's probably riding her bike.
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