What Is VoIP Security Testing?

VoIP (Voice over Internet Protocol) is the communications technology that carries voice over IP networks. Today the majority of IP PBX systems, call centres, SIP trunk infrastructures, video conferencing systems and corporate communication platforms run on VoIP.

A VoIP security test (VoIP penetration test) is a comprehensive penetration testing service carried out to assess the security posture of SIP infrastructure, IP PBX systems, VoIP servers and voice communication platforms.

The assessment goes well beyond SIP services: authentication mechanisms, user accounts, call routing processes, voice traffic (RTP), management interfaces, the VoIP network infrastructure and the communication protocols themselves are all analysed using genuine attacker techniques.

The objective is to identify and verify the vulnerabilities that could lead to unauthorised access, toll fraud, call interception, service disruption (DoS/DDoS), account takeover and manipulation of voice communications.

SecureSys VoIP security tests are conducted in line with OWASP, PTES, NIST and SIP/RTP security standards.

Why Should You Run a VoIP Security Test?

Because VoIP systems are exposed to the internet, they are among the corporate systems attackers target most frequently.

A misconfigured IP PBX or SIP server can lead to:

Free international calls placed at your expense (toll fraud)
Calls being intercepted
Voice recordings being stolen
User accounts being compromised
Call centres being taken out of service
Disruption to corporate communications
Financial loss
Breaches of personal data

A VoIP security test surfaces these risks before attackers find them, so the appropriate technical controls can be applied.

What Is VoIP (Voice over IP) Technology?

VoIP is the communications technology that carries voice over IP-based networks instead of traditional telephone lines. Organisations are migrating from classic PBX systems to IP-based telephony for lower cost, more flexible administration and better support for remote work.

VoIP covers far more than IP handsets: call centres, SIP trunk services, Microsoft Teams Phone, Cisco Unified Communications, Zoom Phone, 3CX, Asterisk, FreePBX and cloud-based telephony platforms all fall within its scope.

Because VoIP systems are reachable over the internet, they carry significant cyber risk. A misconfigured VoIP infrastructure can both interrupt corporate communications and cause serious financial loss.

How Do VoIP Systems Work?

In a VoIP infrastructure, voice is converted into digital data packets rather than an analogue signal and transmitted across the IP network. Several protocols work together to make this happen.

The principal VoIP components are:

SIP (Session Initiation Protocol)
RTP (Real-time Transport Protocol)
SRTP (Secure Real-time Transport Protocol)
SIP trunk
IP PBX
Softphone applications
IP handsets
Session Border Controller (SBC)
Voicemail servers
Call manager

A weakness in any one of these components can affect the entire communications infrastructure.

The Most Common Security Risks in VoIP Infrastructure

Because VoIP systems carry voice traffic over the internet, they are exposed not only to conventional network attacks but also to threats specific to communication protocols.

The most common VoIP security risks are:

SIP username and extension enumeration
SIP brute force attacks
Default usernames and passwords
Toll fraud (unauthorised chargeable calls)
SIP registration hijacking
SIP spoofing
Interception of RTP traffic
Call hijacking
Unauthorised call forwarding
Voicemail access
SIP flood and INVITE flood attacks
UDP flood
Denial of service (DoS/DDoS)
Vulnerabilities in management interfaces
Out-of-date PBX software

These risks lead not only to communication outages but also to inflated telephone bills, data breaches and reputational damage.

What Is Toll Fraud?

Toll fraud is one of the most common attacks against VoIP systems. Using compromised SIP accounts or IP PBX access, attackers place calls to international, premium-rate or chargeable numbers, leaving the organisation with a very large telephone bill.

Most toll fraud takes place overnight or during public holidays, and the losses can be substantial by the time the organisation notices.

As part of SecureSys VoIP security testing, SIP accounts, dialling permissions, call routing policies and chargeable-call scenarios are analysed under controlled conditions.

What Is the SIP Protocol?

SIP (Session Initiation Protocol) is the standard signalling protocol used in VoIP to establish, manage and terminate calls.

SIP handles:

Call setup
Call termination
User registration
Authentication
Call forwarding
Video calls
Conference calls

When SIP services are exposed to the internet they can be scanned by attackers, and weak configurations can lead directly to a breach.

What Are RTP and SRTP?

RTP (Real-time Transport Protocol) is the core VoIP protocol that carries voice and video packets in real time.

When standard RTP traffic is not encrypted, an attacker on the same network can capture the voice packets and listen in on conversations.

For this reason, modern VoIP infrastructures should encrypt voice traffic using SRTP (Secure Real-time Transport Protocol).

SecureSys testing analyses RTP and SRTP configuration to assess the confidentiality of voice communications.

IP PBX Security

IP PBX systems are the central component managing an organisation's telephony. Their management interfaces, SIP user accounts, voicemail systems and call routing services make them high-value targets.

The following checks are performed during security testing:

Administrative interface security
Default user accounts
Password policy strength
Authorisation controls
SIP user management
Call routing rules
Patch level
Logging and call detail records
Remote access configuration

Session Border Controller (SBC) Security

A Session Border Controller is a critical security component that mediates communication between the internal network and the outside world in a VoIP infrastructure.

SBC solutions:

Filter SIP traffic
Perform authentication
Manage NAT traversal
Mitigate DoS and DDoS attacks
Enforce call policies
Support secure media streams

SecureSys also analyses SBC configuration and security policy in depth, assessing how resilient the VoIP infrastructure is to external threats.

Scope of the Service

SecureSys VoIP security testing covers the following components.

SIP security testing

SIP registration
SIP authentication
SIP enumeration
SIP INVITE
SIP OPTIONS
SIP BYE
SIP CANCEL
SIP REFER
SIP MESSAGE
SIP header analysis

RTP Security

RTP traffic analysis
SRTP verification
Voice packets
Call interception risk
Media security

IP PBX Platforms Covered

Asterisk
FreePBX
3CX
Cisco Unified Communications
Avaya IP Office
Yeastar
Grandstream UCM
Issabel PBX
Elastix
FreeSWITCH

SIP Trunk Security

SIP provider configuration
Trunk authentication
IP access control lists
Registration security
SIP TLS

Management Interface Security

Web management interface
Authentication
Authorisation
MFA controls
Default accounts
Privilege escalation scenarios

Network Security

VLAN segregation
Voice VLAN
QoS configuration
Firewall rules
NAT design
VPN integration

Vulnerabilities Covered

SecureSys VoIP security testing analyses the following vulnerability classes.

Authentication

Weak passwords
Default credentials
Brute force
Password spraying
Credential stuffing

SIP Security

SIP enumeration
SIP registration hijacking
SIP spoofing
SIP replay
SIP message manipulation

Call Security

Toll fraud
Call hijacking
Call forward manipulation
Unauthorised call routing
Premium number abuse

Voice Security

RTP sniffing
RTP injection
Missing SRTP
Call recording risks
Voice eavesdropping

Management Security

Authentication bypass
Broken access control
Session hijacking
CSRF
XSS
SQL injection
Command injection

DoS and DDoS

SIP flood
INVITE flood
REGISTER flood
OPTIONS flood
RTP flood
UDP flood
TCP flood

The VoIP Security Testing Process

Scoping
VoIP infrastructure discovery
SIP service analysis
User and extension discovery
Authentication testing
Authorisation analysis
Call scenarios
Toll fraud testing
RTP security analysis
DoS / DDoS resilience testing
Risk analysis
Technical and executive reporting
Retest

What You Receive at the End of the Test

Executive summary
Technical VoIP security test report
SIP security analysis
RTP traffic analysis
Toll fraud risk assessment
Authentication findings
Authorisation findings
Proof-of-concept evidence
CVSS risk scores
Remediation recommendations
Retest results

Which Organisations Need VoIP Security Testing?

This service is particularly recommended for:

Call centres
Banks and financial institutions
Public sector institutions
Healthcare providers
Telecom operators
Defence industry
Energy companies
Universities
Large enterprises
Businesses running an IP PBX
Organisations using SIP trunk infrastructure
Companies on Microsoft Teams Phone, Cisco UC and similar enterprise communication platforms

Why SecureSys?

VoIP security cannot be established by scanning SIP ports. A genuine assessment requires call management, authentication, SIP signalling, RTP media traffic, management interfaces and the underlying network to be analysed together.

At SecureSys we carry out VoIP security testing using real attacker techniques, evaluating SIP infrastructure, IP PBX systems, call centres and corporate communication platforms end to end. We simulate toll fraud, SIP spoofing, call interception, account takeover and service disruption under controlled conditions, and deliver verified findings with remediation guidance you can act on.

The SecureSys Difference

Expert penetration testing under TSE TS 13638
Comprehensive security analysis of the SIP and RTP protocols
End-to-end assessment of IP PBX, SIP trunk and VoIP infrastructure
Toll fraud and call manipulation scenarios
SIP flood and VoIP DoS/DDoS testing
Manually verified security findings
Detailed reporting at both technical and executive level
Risk prioritisation and retest support

VoIP Security Testing Service