According to ITWorldCanada.com, adjusting firewalls for premium Voice over Internet Protocol (VoIP) traffic makes remote access easier for a telework environment, but can also create security vulnerabilities that jeopardize the entire network.

Hackers can access a network by finding VoIP server addresses on Google or by scanning for commonalities in mail server protection lists. If users do not change default settings, hackers could use a vendor's Web site to find usernames and passwords in installation documentation. Hackers can also record conversations from IP phones with packet-capture, depending on the type of encryption. Session initiated protocol (SIP) 1.0 can be easily decoded whereas SIP 2.0 is far more difficult. Users with default answering machine messages are also vulnerable because the messages let hackers know what brand IP phone system is being used and plan their reconnaissance and attacks accordingly. VoIP phones contain the same vulnerabilities as any other IP application, and users need to maintain the same precautions they would with online banking. The solution is to disable VoIP Web servers and change default usernames, passwords, and voicemail greetings.