Common Attack Pattern Enumeration and Classification
A Community Resource for Identifying and Understanding Attacks
This type of attack against older telephone switches and trunks has been around for decades. A tone is sent by an adversary to impersonate a supervisor signal which has the effect of rerouting or usurping command of the line. While the US infrastructure proper may not contain widespread vulnerabilities to this type of attack, many companies are connected globally through call centers and business process outsourcing. These international systems may be operated in countries which have not upgraded Telco infrastructure and so are vulnerable to Blue boxing. Blue boxing is a result of failure on the part of the system to enforce strong authorization for administrative functions. While the infrastructure is different than standard current applications like web applications, there are historical lessons to be learned to upgrade the access control for administrative functions.
An adversary identifies a vulnerable CCITT-5 phone line, and sends a combination tone to the switch in order to request administrative access. Based on tone and timing parameters the request is verified for access to the switch. Once the adversary has gained control of the switch launching calls, routing calls, and a whole host of opportunities are available.
Skill or Knowledge Level: Low
Given a vulnerable phone system, the attackers' technical vector relies on attacks that are well documented in cracker 'zines and have been around for decades.
CCITT-5 or other vulnerable lines, with the ability to send tones such as combined 2,400 Hz and 2,600 Hz tones to the switch
Implementation: Upgrade phone lines. Note this may be prohibitively expensive
Use strong access control such as two factor access control for administrative access to the switch
[R.5.1] [REF-2] G. Hoglund and G. McGraw. "Exploiting Software: How to Break Code". Addison-Wesley. February 2004.
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