Top 14 VoIP vulnerabilities

How are VoIP networks weak and vulnerable to attack and catastrophic failure? Securing VoIP Networks, the new book by Peter Thermos and Ari Takanen, looks at VoIP infrastructure and analyzes its vulnerabilities much as the Open Web Application Security Project did for Web-related vulnerabilities and Mitre did with its Common Weakness Enumeration dictionary for software. And it’s about human failings, too, not just technology problems.

Here are the top VoIP vulnerabilities explained in Securing VoIP Networks:

1. Insufficient verification of data: In VoIP implementations, this can enable man-in the-middle attacks.

2. Execution flaws: Standard databases are typically used as the backbone of VoIP services and registrations. Implementation has to be paranoid in filtering out active content such as SQL queries from user-provided data such as user names, passwords, and Session Initiation Protocol (SIP) URLs. The majority of problems relating to execution flaws result from bad input filtering and insecure programming practices.

3. String/array/pointer manipulation flaws: Malformed packets with unexpected structures and content can exist in any protocol messages, including SIP, H.323, SDP, MGCP, RTP, and SRTP. Most typical malformed messages include buffer-overflow attacks and other boundary-value conditions. The result is that the input given by the attacker is written over other internal memory content, such as registers and pointers, which will let the attacker take full control of the vulnerable process.

4. Low resources: Especially in embedded devices, the resources that VoIP implementations can use can be scarce. Low memory and processing capability could make it easy for an attacker to shut down VoIP services in embedded devices.

5. Low bandwidth: The service has to be built so that it will withstand the load even if every caller makes a call at the same time. When the number of subscribers to a VoIP service is low, this is not a big problem. But when a service is intentionally flooded with thousands of bot clients, or when there is an incident that results in a huge load by valid subscribers, the result might be a shutdown of the whole service.

6. File/resource manipulation flaws: These are typical implementation mistakes, programming errors from using insecure programming constructs that result in security problems. These flaws include insecure access to files.

7. Password management: The only identifier a VoIP consumer has is the telephone number or SIP URL and a possible password for the service. The passwords are stored in both the client and server. If passwords are storied in the server in a format that can be reversed, anyone with access to that server (or proxy or registrar) can collect the username and password pairs.