With so much coverage centering on breakins of enterprise computer networks, there is a chance that some corporations and government agencies may be neglecting the lowly office phone. And that may be a costly mistake.

One recent example: the phone systems of Bell County in Texas has been hacked between November 30 and December 2, 2013. A few days were enough for the attackers to make international phone calls worth over $27,000.

The attackers abused a weak 4 digit password in one of the county departments. The hackers routed calls to Grenada, a country in the Caribbean.

In October, the county paid $855 for phone services. However, for one day while the hackers had access to systems, the bill was more than $27,220.

County representatives say they have implemented measures to prevent future incidents. However, on December 13, another breach was detected. On this occasion, Bell County was notified of the intrusion by telephone carrier security officials.