VoIP isn’t immune to several security threats, especially now that scammers and phishers have several ways to capitalize on the technology. Nevertheless, knowing what these potential attacks are will make you more alert and responsible in using the system.

DoS Dodging

This is considered to be the most serious and thus dangerous malicious VoIP attack. It can stop your IP handset from working, cause the server to crash, and extremely slow down your productivity. Worse, it leaves your entire network compromised.

This threat is so difficult to address immediately since hackers usually employ a very slow approach. But you can greatly reduce the risk and prevent it from affecting a large part of your network by downloading, installing, and updating your firewall and anti-virus software.


This is the abbreviated form for VoIP phishing. Phishers can tap into your network and send you a message via a voice synthesis. Sometimes it spoofs numbers, so you’ll be forced to believe that it’s a legitimate call. The “call” may be from a credit card company, lender, or bank; the bottom line is, if you’re not careful, you’ll share your critical personal information such as your bank accounts, credit cards, name, and address.

To reduce exposure in vishing, don’t call the number often left by the phisher. Instead, dial the valid telephone numbers of companies they claim they’re a part of and inquire about the details of the call.


Spit is spam over IP telephony. Though this isn’t as popular as DoS or vishing, it can be a prelude to any of mentioned threats. Fortunately, since e-mail anti-spam applications won’t work in spit, companies such as NEC have developed VoIP-specific tools like VoIP Seal.