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Communication Security: Wireless • Chapter 4 221

Protecting Against Sniffing and Eavesdropping

As networking technology matured, wired networks were able to upgrade from
repeaters and hubs to a switched environment.These switches would send only the
traffic intended for a specific host over each individual port, making it difficult
(although not impossible) to sniff the entire network’s traffic. Unfortunately, this is
not an option for wireless networks due to the nature of wireless communications.
The only way to protect wireless users from attackers who might be sniffing is
to utilize encrypted sessions wherever possible: SSL for e-mail connections, SSH
instead of Telnet, and Secure Copy (SCP) instead of File Transfer Protocol (FTP).
To protect a network from being discovered with NetStumbler, it is important
to turn off any network identification broadcasts and, if possible, close down the
network to any unauthorized users.This prevents tools such as NetStumbler from
finding the network. However, the knowledgeable attacker will know that just
because the network is not broadcasting information, does not mean that the net-
work cannot be found.
All an attacker needs to do is utilize one of the network sniffers to monitor for
network activity.Although not as efficient as NetStumbler, it is still a functional
way to discover and monitor networks. Even encrypted networks show traffic to
the sniffer. Once they have identified traffic, the attacker can then utilize the same
identification techniques to begin an attack on the network.

Spoofing (Interception)
and Unauthorized Access

The combination of weaknesses in WEP and the nature of wireless transmission has
revealed spoofing to be a real threat to wireless network security. Some well-publi-
cized weaknesses in user authentication using WEP have made authentication
spoofing just one of an equally well-tested number of exploits by attackers.
One definition of spoofing is the ability of an attacker to trick network equip-
ment into thinking that the address from which a connection is coming is a valid
machine from its network.Attackers can accomplish this in several ways, the easiest
of which is to simply redefine the MAC address of the attacker’s wireless or net-
work card to be a valid MAC address.This can be accomplished in Windows
through a simple Registry edit. Several wireless providers also have options available
to define the MAC address for each wireless connection from within the client
manager application that is provided with the interface.

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