2 cissp ® Official Study Guide Eighth Edition

War Chalking
War chalking
is a type of geek graffiti that some wireless hackers used during the early 
years of wireless (1997–2002). It’s a way to physically mark an area with information about 
the presence of a wireless network. A closed circle indicated a closed or secured wireless 
network, and two back-to-back half circles indicated an open network. War chalking was 
often used to disclose to others the presence of a wireless network in order to share a dis-
covered internet link. However, now that internet connectivity is nearly ubiquitous, with 
most of us carrying an internet-connected device on our person (usually a smartphone), 
the popularity of portable Wi-Fi hotspots, and many retail establishments offering free 
Wi-Fi as an incentive for customers, the need for and occurrence of war chalking has faded. 
When an attacker uses war dialing to locate a wireless target to compromise, they don’t 
mark up the area with special symbols to inform others of their intentions.

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Chapter 11 
■
Secure Network Architecture and Securing Network Components
Replay
A 
replay attack
is the retransmission of captured communications in the hope of gaining 
access to the targeted system. Replay attacks in relation to wireless environments specifi-
cally may continue to focus on initial authentication abuse. However, many other wireless 
replay attack variants exist. They include capturing new connection requests of a typical 
client and then replaying that connect request in order to fool the base station into respond-
ing as if another new client connection request was initiated. Wireless replay attacks can 
also focus on DoS by retransmitting connection requests or resource requests of the base 
station in order to keep it busy focusing on managing new connections rather than main-
taining and providing service for existing connections.
Wireless replay attacks can be mitigated by keeping the firmware of the base station 
updated as well as operating a wireless-focused network intrusion detection system (NIDS). 
A 
W-IDS
or 
W-NIDS
will be able to detect such abuses and inform the administrators 
promptly about the situation.
IV
IV
stands for 
initialization vector
, a mathematical and cryptographic term for a random 
number. Most modern crypto functions use IVs to increase their security by reducing 
predictability and repeatability. An IV becomes a point of weakness when it’s too short, 
exchanged in plain text, or selected improperly. Thus, an IV attack is an exploitation of 
how the IV is handled (or mishandled). One example of an IV attack is that of cracking 
Wireless Equivalent Privacy (WEP) encryption.
WEP is the original encryption option of 802.11 wireless networking. It’s based on 
RC4. However, because of mistakes in its design and implementation, WEP’s primary flaw 
is related to its IV. The WEP IV is only 24 bits long and is transmitted in plaintext. This, 
coupled with the fact that WEP doesn’t check for packet freshness, allows a live WEP crack 
to be successful in less than 60 seconds (see the Wesside-ng tool from the Aircrack-ng suite 
at 
www.aircrack-ng.org
).