Checking for Live Systems 107
Modems and dial-up are still used as a backup to existing technologies
such as cable, digital subscriber lines (DSL), and T1 and T3 lines. The idea
is that if all other connectivity options fail, the phone lines should still be
available barring a major accident or outage. Companies find the low cost
and reliability of the technology to be a nice safety net to have in the event
of an outage.Once you find a modem and get a response, the question becomes what to do with
that information. To answer that, you need to know what devices modems are
commonly attached to in the modern world. Private branch exchanges (PBXs) often have
modems attached (the nondigital ones), which can provide a good opportunity for mischief
on behalf of the attacking party. Other devices that sometimes have modems attached are
firewalls, routers, and fax machines. If an attacker dials into a firewall and gains access, an
environment can quickly become unprotected.
A modem should always be considered a viable backdoor access method
to a given environment because they are frequently used that way by their
owners. Although Grandma and Grandpa may still use them to access the
Internet, they are more frequently seen as methods to access a network
when all other means are unavailable.A number of wardialing programs have been created over the years. Here are three of
the best-known ones:
To n e L o c A wardialing program that looks for dial tones by randomly dialing numbers or
dialing within a range. It can also look for a carrier frequency of a modem or fax. ToneLoc
uses an input file that contains the area codes and number ranges you want it to dial.
THC-SCAN A DOS-based program that can use a modem to dial ranges of numbers in
search of a carrier frequency from a modem or fax.
NIKSUN’s PhoneSweep One of the few commercial options available in the wardialing
market.
Wardialing still works as a valid penetration method into an organization for several
reasons, but let’s focus on one of the bigger reasons: the lack of attention or respect these
devices get. You may see wardialing or modems as ancient technology, conjuring mental
images of slow connections, screeching connections, and dial-up services such as AOL and
CompuServe. Although these ancient images are valid, don’t let them lull you into a false
sense of security. In today’s corporate world, it is not uncommon to find these devices not
only present, but in many cases completely unmonitored or even unrecorded, meaning they
are off the radar. In many cases, modems exist within a given environment for years until
someone in accounting asks why the company is paying for a dial-up connection or who a
certain phone number is assigned to.