Holiday VoIP Fraud Prevention Guide for Businesses

According to industry reports, VoIP fraud costs businesses billions of dollars globally each year, and the risk spikes during holidays when offices are empty and systems are left unattended. For organizations relying on cloud voice and connectivity, understanding this threat is critical to protecting uptime and revenue. At 1Wire, we see firsthand how the right network foundation helps prevent these issues before they start.

In simple terms, VoIP fraud happens when criminals break into your phone system and use it to make expensive calls that you pay for. For example, a small business in Salt Lake City might close its office for the holidays, only to come back in January to find thousands of dollars in unauthorized international calls on its bill. They usually do this after hours or during holidays, when no one is watching. The result can be massive phone bills and busy phone lines when customers or staff need to reach you most.

Key Takeaways

• What VoIP fraud and toll fraud are, and why they matter to non-technical teams

• How attackers exploit exposed phone systems behind the scenes

• Why holidays are a favorite time for fraudsters

• The business continuity risks beyond just a high phone bill

• How firewalls, VoIP settings, and internet quality reduce risk

• A practical pre-holiday checklist to lock down your phone system

What VoIP and toll fraud are

Voice over IP (VoIP)—sometimes referred to as Cloud Phones—allows your business to make calls over the internet instead of traditional phone lines. Desk phones, softphones, and call center platforms all register to a VoIP phone system (PBX), which then connects to the outside world through your carrier. That flexibility is ideal for remote and hybrid work—but it also creates new opportunities for misuse if systems are not properly secured.

Toll fraud (also known as VoIP fraud or International Revenue Sharing Fraud) occurs when attackers gain unauthorized access to your phone system and place calls to high-cost destinations, such as international or premium-rate numbers. They are not trying to contact your staff, they are trying to generate charges that appear on your bill. In extreme cases, just a few days of fraudulent calls can result in tens of thousands of dollars in unexpected costs.

How VoIP fraud works behind the scenes

Fraudsters typically begin by scanning the internet for exposed VoIP services. This can include open SIP ports, phones or PBXs reachable from the public internet, or remote management interfaces. They then test default passwords, weak credentials, or unpatched software until they find a way in.

Once access is gained, attackers automate large volumes of outbound calls to expensive destinations they control or profit from. These calls usually run overnight, on weekends, or during holiday closures, times when call logs and alerts are less likely to be reviewed. Because VoIP shares your internet connection, this activity can also consume bandwidth and call capacity, blocking legitimate calls.

Why the holidays are a prime target

The holidays are ideal for VoIP fraud because oversight drops while systems stay online. Fewer employees are monitoring activity, IT and finance teams are on limited schedules, and unusual charges may not be noticed until well after the break.

If an attack begins on Christmas Eve or over a long holiday weekend, it can continue for days unchecked. Imagine a retail or healthcare office along the Wasatch Front—whether in Ogden, Provo, or Lehi—missing critical calls because phone lines are tied up with fraudulent traffic. During that time, your phone lines may be tied up, preventing customers, partners, or on-call staff from reaching your business, directly impacting service and revenue.

How this affects business continuity

VoIP fraud is not just a billing problem, it is a continuity risk. Utah businesses that rely on phones for appointments, deliveries, or after-hours support—such as clinics in Utah County or service companies in Davis County—can feel the impact almost immediately. Large volumes of unauthorized calls can overwhelm your available call paths, causing busy signals or failed calls for legitimate users. For sales, support, healthcare, or emergency-response organizations, this disruption can be severe.

Recovery also takes time. IT teams must investigate how access was gained, secure the system, and work with carriers to dispute charges. In some industries, incidents must be documented for compliance or audits, extending the disruption even further.

How firewalls help stop VoIP fraud

A properly configured firewall is a critical first line of defense. Modern firewalls can recognize SIP traffic, inspect call setup messages, and restrict VoIP access to trusted carriers and locations. This dramatically reduces exposure to random internet scanning.

At a minimum, your firewall should:

• Block VoIP access from all locations except trusted carriers, offices, and VPNs
• Use Geo-IP filtering to deny traffic from countries you never call
• Log and alert on repeated failed registrations or unusual call bursts

Administrative access to your phone system should never be open to the public internet. Restricting management access to VPNs or internal networks significantly lowers risk.

If you’re looking to simplify your security over the holidays, learn more about our Managed Firewall service.

VoIP configuration settings that prevent unauthorized calls

Even with a strong firewall, internal VoIP configuration matters. Focus on authentication, dial plans, call limits, and feature controls.

Strong authentication and access control

• Use strong, unique passwords for every extension and admin account
• Disable unused extensions and remove default accounts
• Restrict extensions to approved devices or IP ranges when possible

Tight outbound dial plans

• Avoid broad dialing rules that allow any number
• Block international and premium-rate destinations you do not need
• Only enable country codes relevant to your business

Call and route limits

• Set limits on concurrent calls per extension and trunk
• Apply daily minute or spend thresholds for high-risk routes
• Require PINs for expensive destinations

Time-of-day and feature controls

• Limit after-hours calling to essential numbers only
• Disable or tightly control external call forwarding, DISA, and call-through features

Not sure how to apply these changes? Contact our support staff and have them help you lock up for the holidays.

Why a good internet connection matters

VoIP depends on your internet connection. A stable, business-grade connection with Quality of Service (QoS) ensures voice traffic remains clear and reliable—even during spikes or attacks. Reliable connectivity also makes it easier to enforce security measures like VPN-only admin access, encryption, and real-time monitoring.

When connectivity is unreliable, teams are more likely to bypass security controls for convenience, increasing exposure to fraud and outages.

If you’re looking for the best, most reliable internet in Utah, learn more about our Business Internet.

Steps to take before leaving for the holidays

Before closing the office, treat your VoIP system like your physical building: lock it, test it, and set alarms. Just as you would not leave a storefront in downtown Salt Lake City or a warehouse in West Valley unlocked over a holiday weekend, your Cloud Phones deserve the same attention.

• Review outbound rules and block unused international and premium routes
• Apply stricter after-hours policies for holidays and weekends
• Disable risky features such as external call forwarding unless required
• Audit extensions, reset weak passwords, and remove unused accounts
• Restrict admin access to VPNs or known IPs only
• Configure real-time alerts for unusual calling patterns
• Confirm an on-call response plan if fraud is detected after hours

Running a short tabletop exercise—asking who responds and how—can make the difference between a minor incident and a major outage.

FAQs

What is VoIP fraud?

VoIP fraud is when attackers gain unauthorized access to a phone system and use it to place expensive calls that appear on the business’s phone bill.

Why does VoIP fraud increase during holidays?

Because offices are closed, monitoring is reduced, and attacks can run longer before being detected.

Can a firewall alone stop VoIP fraud?

A firewall is essential, but it must be combined with strong VoIP configuration, access controls, and monitoring.

How quickly can VoIP fraud become expensive?

In some cases, fraudulent calls can generate thousands of dollars in charges within hours.