devices (e.g., AirMagnet [4] and NetStumbler [5]), forcing IT
personnel to walk the halls of the enterprise or campus
searching for rogue APs. This method is generally ineffective
because manual scans are time-consuming and expensive –
and, therefore, are conducted infrequently. Also, with 802.11
hardware operating at separate frequencies (802.11a - 5Ghz
and 802.11b - 2.4Ghz), IT personnel must upgrade their
detection devices to accommodate multiple frequencies.
Moreover, scans are easy to elude, since a rogue AP can
easily be unplugged when the scan takes place.
Most vendors today go a step further. Rather than relying
on an employee equipped with a scanner, they enable IT to
initiate an enterprise-wide scan from a central location. This
is possible by using separate hardware devices [2][3][7][8]
(e.g., sensors) or using APs to detect beacons from
surrounding APs [2], and transmitting this information back
to a central management platform containing the wireless
network policy for analysis [1]. This method becomes costly,
considering that one must place sensors or APs throughout
the entire enterprise to monitor the air waves. This technique
is also completely impractical for the networks that do not
have wireless APs. Much like the drawback of the “walking
the halls” solution, each sensor/AP must operate at both
frequencies to be completely effective. Moreover, with
sensors deployed throughout the network, one still may not
be able to detect the rogue AP. The clever employee could
have used a directional antenna, or reduced the signal
strength to cover the small range within his/her office.
Another drawback of wireless-based solutions is that they
will falsely report the wireless network in the coffee house
next door as a rogue.
B. Hybrid Wireless and Wired Approach
Taking a step in the right direction, Wavelink [2] combined
the previously mentioned techniques for detecting Rogue APs
with listening at network layers 2 and 3 and querying
switches and routers to determine what devices are connected
to them, thus, attempting to provide a hybrid wired and
wireless approach to detecting Rogue APs. This fails for the
same reasons that the wired-only solutions discussed in detail
below fail.
C. Wired Approaches
Cisco offers a more complete, scalable, and comprehensive
approach using a suite of tools [9] that are not limited by
signal range. They attempt to detect APs by querying routers
and switches for company MAC address assignments (i.e., if
the MAC address belongs to Linksys, the MAC address
cannot belong to a PC and becomes suspicious). This fails
because MAC addresses can be spoofed or cloned easily by
an AP. Another approach in the suite is the use of httpd
query to communicate with the web server residing on the
AP. This is a good approach, but the node must already be
suspected as being an AP (maybe using one of the
aforementioned methods), or every node on the network must