A phone call displaying a familiar number is not necessarily coming from the person or organisation associated with it. Caller ID spoofing exploits this gap between what recipients see and where a call actually originates, creating challenges for telecom providers and their customers.
For carriers, detecting spoofed calls requires more than identifying suspicious phone numbers. It involves examining call authentication data, signalling information, traffic patterns and the behaviour of upstream providers. Technologies such as STIR/SHAKEN help establish trust in caller ID information while network analytics and traceback processes provide additional ways to identify suspicious traffic. PeeringHub supports this ecosystem through STIR/SHAKEN certificate infrastructure, Identity Header analysis and certificate validation tools.
Understanding Caller ID Spoofing and Why It Matters
Caller ID spoofing occurs when a caller deliberately presents a telephone number that does not accurately identify the actual source of the call. The displayed number may belong to an individual, a business, a government organisation or even the person receiving the call.
Why Do Fraudsters Use Spoofed Caller IDs?
The primary objective is to make an unfamiliar or fraudulent call appear trustworthy. A recognised number can increase the likelihood that someone answers and engages with the caller.
Common motivations include:
Financial fraud: Impersonating banks, payment providers or financial institutions to gain access to sensitive information.
Business impersonation: Displaying a company's customer support or sales number to appear legitimate.
Government impersonation: Using numbers associated with public institutions to create urgency or authority.
Robocall campaigns: Making large volumes of unwanted calls appear to originate from different or familiar numbers.
Reputation manipulation: Using legitimate numbers to disguise the source of unwanted calling activity.
For example, a recipient may see what appears to be a call from their bank's published customer service number. The displayed number alone does not establish that the bank actually placed the call.
The Government Accountability Office has identified fake caller ID schemes as a recurring method used in scams involving money and personal information. This makes caller ID integrity an important part of telecom network security.
The Most Common Caller ID Spoofing Techniques
Spoofing can occur in different ways depending on the calling infrastructure, network path and type of fraud being attempted. Carriers need to understand these patterns to build effective detection strategies.
Neighbour or Local Number Spoofing
Neighbour spoofing involves displaying a number with an area code or prefix similar to the recipient's own number. The familiarity can make the incoming call appear local.
Example: A customer receives a call from a number that shares the same first six digits as their own number. They may assume it is from a neighbour or local business.
Detection approach: Carriers can examine calling patterns, number allocation information and traffic volumes. Repeated calls using similar number ranges across unrelated campaigns may indicate suspicious activity.
Impersonation of Trusted Organisations
Fraudsters may display numbers associated with banks, government offices, healthcare providers or well-known businesses.
Example: A call appears to come from a bank's published number but the actual calling source is unrelated to that institution.
Detection approach: Carriers can compare the claimed calling number with authentication results and available number-authorisation information. A failed or missing authentication result may warrant further investigation, although it does not automatically prove fraud.
Randomised or Rotating Caller ID Spoofing
Some unwanted calling campaigns use multiple displayed numbers to make traffic harder to identify through simple number-based filtering.
Example: A high-volume campaign generates calls using many different caller IDs over a short period. Blocking one number does not necessarily stop the wider campaign.
Detection approach: Traffic analytics can identify patterns across call volume, duration, timing, destinations and upstream sources. Analysing a campaign rather than an individual number can reveal activity that basic blocking rules may miss.
International Gateway and Origin Masking
Calls can pass through multiple networks before reaching their destination. In some cases, an international or gateway provider may receive traffic carrying misleading caller ID information.
Example: A call appears to originate from a domestic business number even though the traffic entered the country through an international network.
Detection approach: Providers can examine gateway information, authentication status and upstream routing records. Traceback procedures can help identify the provider that introduced suspicious traffic into the network.
VoIP and Compromised Calling Infrastructure
Internet-based voice services provide legitimate flexibility for businesses and telecom operators. However, compromised accounts, misconfigured systems or abusive service providers can also become sources of spoofed traffic.
Example: A compromised business calling account is used to generate calls that display numbers unrelated to the account holder.
Detection approach: Carriers can monitor abnormal traffic volumes, unusual calling destinations, authentication failures and changes in established calling behaviour. Account-level investigation may be necessary to identify the source.
These techniques demonstrate why number reputation alone is insufficient. Effective detection requires multiple sources of information and a view of the wider call path.
How Carriers Detect Caller ID Spoofing
Carriers combine call authentication, traffic analytics and network investigation to identify suspicious calling activity. No single technique can detect every form of spoofing.
STIR/SHAKEN Call Authentication
STIR/SHAKEN is a framework designed to authenticate caller ID information in IP-based voice networks. It uses digital certificates and cryptographic signatures to help verify whether the calling number information presented with a call is supported by the originating provider's knowledge and authority.
The originating provider creates a signed PASSporT identity token and includes it in the SIP Identity header. The receiving provider can then use the associated certificate to validate the signature and examine the authentication information.
Three attestation levels communicate the originating provider's level of confidence:
A – Full Attestation: The provider knows the customer and has verified the customer's authority to use the calling number.
B – Partial Attestation: The provider knows the customer but cannot verify the customer's authority to use the specific calling number.
C – Gateway Attestation: The provider can identify the point where the call entered its network but does not have a direct relationship with the original caller.
These levels are not universal fraud scores. A B or C attestation does not automatically mean a call is fraudulent and an A attestation does not guarantee that the call is safe.
The FCC describes STIR/SHAKEN as a mechanism for authenticating caller ID information and supporting other robocall mitigation tools rather than a complete solution to illegal calls.
Call Pattern and Traffic Analytics
Authentication data becomes more useful when combined with network-level analytics.
Carriers can examine:
Unusual increases in outbound call volume.
Repeated calls to large groups of unrelated destinations.
High call rates from newly observed sources.
Abnormal call duration and completion patterns.
Repeated authentication failures.
Traffic associated with known suspicious upstream providers.
For example, a provider may receive thousands of calls displaying different local numbers within a short period. Although each number may appear different, shared traffic characteristics can indicate that the calls belong to one campaign.
This is why modern detection systems need to evaluate both individual calls and broader traffic behaviour.
Using Identity Headers, Certificate Validation and Traceback
STIR/SHAKEN provides authentication information, but carriers must also be able to inspect and interpret that information accurately.
Inspecting the SIP Identity Header
The SIP Identity header contains the signed PASSporT token and information used to locate the originating provider's certificate. Its contents can help a receiving provider understand the call's authentication context.
PeeringHub provides an Identity Header Parser that allows users to decode a STIR/SHAKEN Identity header and inspect important fields, including:
Attestation level.
Origination and destination telephone numbers.
Original identifier (origid).
Certificate URL (x5u).
Signing algorithm.
Signature validation status.
This helps technical teams examine authentication information rather than relying only on the caller ID displayed to the recipient. <Cite refs={["turn372214search1","turn372214search0"]}/>
Verifying the Signing Certificate
A valid signature depends on the associated certificate and its trust chain. If the certificate is unavailable, expired or invalid, verification may fail.
PeeringHub's Certificate Inspector allows users to inspect certificate information through pasted certificate content, a certificate URL or an uploaded certificate file. It can return details such as issuer, subject, validity dates and OCN context.
Following the Call Through Network Traceback
Authentication information can also support investigations into suspicious calls. Traceback procedures help providers follow traffic through the network to identify the upstream source.
For example, if a carrier identifies a suspicious call campaign, it can use available call records and provider information to investigate where the traffic entered the network. STIR/SHAKEN information can provide additional context during this process.
Industry approaches combine authentication with Call Detail Record traceback, Do Not Originate databases and analytics.
Why STIR/SHAKEN Alone Cannot Stop Every Spoofed Call
STIR/SHAKEN improves caller ID authentication but it should not be confused with a complete fraud detection or call-blocking system.
Authentication Is Not the Same as Caller Intent
A successful signature verification indicates that the signed information passed the relevant cryptographic checks. It does not establish that the caller has a legitimate reason to contact the recipient.
A fraudster could potentially use a legitimately authorised number or a compromised account. If the originating provider signs the call based on its valid relationship with that number, authentication alone may not reveal the fraudulent intent.
Coverage and Network Limitations
Not every call follows an identical network path. Calls may pass through legacy networks, international gateways or environments where end-to-end authentication information is unavailable.
Carriers therefore need additional detection mechanisms for calls that cannot be fully authenticated.
The Need for Layered Detection
A stronger carrier strategy combines:
STIR/SHAKEN authentication and verification.
Traffic analytics and behavioural monitoring.
Number authorisation and reputation checks.
Do Not Originate list screening where applicable.
Network traceback and upstream provider investigation.
Appropriate call labelling or blocking policies.
The principle is straightforward: authentication helps establish whether caller ID information is supported by the provider's evidence while analytics help assess whether the call's behaviour is suspicious.
The FCC has also recognised that STIR/SHAKEN information can support analytics and call treatment decisions but is not a complete solution to illegal robocalls.
How PeeringHub Supports Carrier-Level Caller ID Authentication
Reliable caller ID authentication depends on a functioning certificate infrastructure and tools that allow technical teams to inspect authentication data.
PeeringHub focuses on STIR/SHAKEN Certificate Authority services and supporting developer utilities that help service providers manage this infrastructure.
STIR/SHAKEN Certificate Authority and ACME Services
PeeringHub operates a STI-ACME server compliant with RFC 8555. Eligible STIR/SHAKEN service providers with their own OCN and approved STI-PA status can subscribe to the CA service and complete the required onboarding process for automated certificate issuance.
Its ACME API supports certificate issuance, renewal and revocation. This helps providers integrate certificate lifecycle operations into their existing systems.
Identity Header Parser and Certificate Inspector
PeeringHub provides tools that help technical teams inspect the authentication information carried in STIR/SHAKEN Identity headers and examine the associated certificates.
These capabilities are useful when investigating signature validation issues, reviewing attestation information or checking certificate details.
STI API and Developer Automation
PeeringHub's STI API supports authentication token generation, private key generation and certificate requests. Its developer-focused tools provide additional options for integrating certificate operations into existing workflows.
Together, these capabilities support the certificate and inspection side of caller ID authentication. They complement carrier analytics, call treatment systems and traceback processes rather than replacing them.
Conclusion: Stronger Caller ID Authentication Starts with Better Network Visibility
Caller ID spoofing continues to challenge telecom providers because fraudulent calls can imitate familiar numbers, exploit network complexity and change their traffic patterns to avoid simple detection methods.
Carriers need a layered approach that combines STIR/SHAKEN authentication, certificate validation, traffic analytics and network traceback. Each method provides a different piece of information and together they create a stronger foundation for identifying suspicious calls.
PeeringHub helps service providers strengthen the STIR/SHAKEN infrastructure behind this process through certificate authority services, ACME automation, Identity Header analysis and certificate inspection tools.
Build a more reliable caller ID authentication workflow with PeeringHub.
Explore the platform and its STIR/SHAKEN solutions at https://www.peeringhub.io/
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