Mobile Phones and VoIP: The Two Devices Cybercriminals Are Counting On You to Ignore

Mobile Phones and VOIP. When we talk about cybersecurity, most businesses jump straight to firewalls, antivirus software, and cloud backups. But there are two pieces of tech almost every employee uses daily that are routinely overlooked — and they’re prime targets for attackers:

➡️ Mobile phones

➡️ VoIP phone systems

Ignore them at your peril — because cybercriminals certainly don’t.

Let’s break down how each is exploited, what damage it can cause, and most importantly, what you can do to lock them down.

Mobile Phones: The Breach You Carry in Your Pocket

Most people assume their smartphones are secure out of the box. After all, there’s Face ID, biometric logins, and encryption, right?

But the reality is very different

How Mobile Phones Get Hacked:

Zero-Click Exploits

These are attacks that don’t require any interaction from the user. Cybercriminals exploit vulnerabilities in messaging apps (like WhatsApp or iMessage) to gain access as soon as the message is received — no tapping, no downloading, no warning.

Public WiFi Hijacking

That free WiFi at the airport or coffee shop? It could be a rogue access point. Hackers set up networks that look legitimate, then monitor or intercept data transmitted over them — including credentials, emails, and app traffic.

QR Code Phishing

Malicious QR codes stuck on menus, posters or windows redirect users to fake websites, capture logins, or silently deliver malware.

Outdated OS and App Vulnerabilities

Unpatched devices are a goldmine. Many users delay installing updates, unknowingly leaving known exploits wide open for attackers.

SIM Swapping

Attackers socially engineer your mobile provider to transfer your number to a new SIM — giving them control of two-factor authentication codes and calls.

What Can Hackers Do With Your Mobile?

• Hijack email accounts

• Bypass multi-factor authentication (MFA)

• Access corporate apps and cloud data

• Track locations or conversations

• Compromise business VoIP systems (see below)

• Launch further attacks on others in your network

A hacked mobile phone isn’t just a personal risk — it’s a corporate entry point.

VoIP Systems: The Backdoor into Your Business

Voice over IP (VoIP) systems have revolutionised business communication — but most are poorly secured. Because they run over the internet, they’re exposed to the same threats as any IT system — and more.

How VoIP Gets Hacked:

Brute Force Attacks on SIP Credentials

If your VoIP phones use SIP (Session Initiation Protocol), attackers can try thousands of username/password combinations to gain control.

Toll Fraud

Once inside, criminals use your system to route calls to premium-rate numbers they control — racking up tens of thousands of pounds in charges.

Eavesdropping and Call Recording

Without encryption, calls can be intercepted. This isn’t science fiction — it’s happening right now. Sensitive client info, trade secrets, payment details — all at risk.

VoIP DDoS Attacks

By overwhelming your VoIP server with traffic, attackers can bring down your phone system — affecting every call, voicemail, and extension.

Voicemail Compromise

Many voicemail boxes are protected by default PINs like “0000” or “1234”. Once inside, attackers can spoof numbers, steal recordings, or impersonate your business.

What Can Hackers Do With Your VoIP System?

• Hijack live calls

• Steal sensitive conversations

• Impersonate your business in outbound calls

• Rack up huge bills in minutes

• Interrupt operations during peak hours

• Use your phone system as a launchpad for deeper attacks

What You Can Do To Stay Protected

Here’s a practical, non-technical checklist — whether you’re a managing director, office manager, or IT decision-maker.

Mobile Phone Security

✅ Enforce Updates — Ensure all devices (personal or company-owned) install OS and app updates automatically.

✅ Use a Mobile Device Management (MDM) Solution — This allows remote wiping, encryption enforcement, and app control across devices.

✅ Disable WiFi Auto-Connect — Especially in public settings. Always verify networks before joining.

✅ Educate Against QR Scanning — Treat QR codes like unknown links. Scan only from trusted sources.

✅ Enable Biometric Locks and Complex PINs — And avoid using birth years or simple patterns.

✅ Restrict App Installations — Only allow installations from official app stores.

✅ Use Security Apps — Business-grade mobile security tools like Lookout or Sophos Intercept X can detect threats early.

VoIP Security

✅ Enforce Strong SIP Passwords — Use complex, unique credentials for every handset or softphone.

✅ Restrict International Call Routing — Only allow outbound calls to necessary countries or ranges.

✅ Use Encrypted Protocols (TLS & SRTP) — This protects call signalling and media from being intercepted.

✅ Monitor Call Volumes and Logs — Unexpected spikes? Unusual destinations? Investigate immediately.

✅ Lock Down Admin Interfaces — Ensure the VoIP system’s web portal is not exposed to the public internet.

✅ Implement IP Whitelisting — Only allow known office or remote IPs to access the VoIP system.

✅ Regularly Update VoIP Firmware — Just like with any other tech, keep it patched and up to date.

The Attack Surface is Expanding

Your business phone system and mobile devices aren’t side issues — they’re core parts of your infrastructure. And because they’re often less protected, they’re more attractive to attackers.

Cybersecurity isn’t just about firewalls and antivirus anymore. It’s about understanding your real-world risks, especially the ones you carry in your pocket or speak into daily.

At Munio, we help UK businesses lock down every layer — from mobile device policies to VoIP hardening and 24/7 threat monitoring.

If you want help understanding how secure (or exposed) your communications are — we’re here.

Want to know how exposed your phones really are?

Take our Cyber Clarity Quiz now and get a plain-English risk score in under 3 minutes.