If your company uses a PBX / Voice Messaging system then you are being targeted by Phreakers (Phone Hackers).

Phreakers take advantage of system interface vulnerabilities, known security (factory) passwords, and use social skills to obtain access to your system resources. Once a phreaker has successfully hacked into your PBX system, he/she may exchange the information with other phreakers, implement Call Back schemes, or place long distance calls that are billed to your company.

Generally, phreakers use auto dialers to scan numbers that answer with carrier signals. When a system answers, it is then compared to the known programming formats. Phreakers will also manually dial into your Voice Messaging system and attempt to breach your systems security features.

Phreakers also recognize