Switching to VoIP

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Chapter 10: Security and Monitoring

The cell phone network has been abused by phreakers, too. Though cell phones have

device-specific electronic serial numbers encoded into their firmware, it is possible,

though difficult, to program an unauthorized phone with a different serial number so

that it can make calls using a legitimate user’s account. This practice is sometimes

called cell phone phreaking. Now, there are better administrative measures to coun-

teract phreaking than there were at the beginning of the cell phone era. Indeed, now

that many of the cell carriers send voice signals digitally, they are able to interleave

and encrypt them so that phreaking is more difficult.

Call Accounting and Billing

When you pick up the phone, dial the pizza place, state your order, and hang up the

phone, a number of call accounting events are recorded. The PSTN, with help from

SS7, records:

• Which number you dialed

• When you dialed the phone number

• When the call was connected

• The duration of the call

• When the call was disconnected

These bits of data are not crucial just to the billing process; they’re also important

because of what they indicate forensically. When a person’s use of the phone system

is used as evidence in court or during disputes between a phone company and its

customers, ...