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Passive attacks are mostly undetectable by network administrators and physical
network devices due to the passiveness of this activity (Curran & Smyth, 2005; Welch
& Lathrop, 2003).
2.5.1.2 Active Attack
Shimonski (2003) stated that the activity of passive attacks could accumulate enough
information leading attackers to actively attack a wireless network. The main target of
active attackers is usually to gain access to a network and then change or modify the
resource’s content (J. Wong, 2003). Two activities that can be categorized as active
attacks are unauthorized access and spoofing (Shimonski, 2003). Active eavesdropping
requires injection of data by the attacker into the communication session in order to
decipher the payload. In this process, the attacker will listens to the wireless connection
while actively injects messages into the communication session in order to determine
the contents of the messages. Active attacks can happen in two ways, the first is when
the attacker modifies a packet. Secondly is when the attackers inject completely new
packets into the data stream (Welch & Lathrop, 2003). Actively attacking the network
can caused the denial of service attack to the WLAN.
2.5.1.3 Denial of Service (DoS attack)
The denial of service attack or sometimes referred to as DoS attack is an effort by
attackers to make a computer resource unavailable to its anticipated users. The
seriousness of this attack is it can cause the network to slow down to a point of being
unusable (Maple, Jacobs, & Reeve, 2006). Even though the motives for DoS attacks, the
means to conduct it, and the targets of such attack varies, it still involves a rigorous and
malicious efforts by the attacker (s) trying to prevent the WLANs services from
functioning properly (Carli, Rosetti, & Neri, 2003). Woodward (2005) explained that
the attack can be attempted in two ways. The first way to conduct the DoS attack is
through the jamming technique which is quite easy to implement and not easily detected.
This attack can cause serious interference to the WLAN when done intentionally or
unintentionally such as placing a device that operates at the same frequency in the
same area as the WLANs. The second way for DoS attack to be done is by exploiting
the authentication and encryption weaknesses that exist within the 802.11 itself (Aime,
Lioy, & Mazzocchi, 2004). In this attack the wireless node is forced to rejoin the
WLANs where the logon and authentication details can be captured while the node is
re-associating itself with the AP. The information gathered from this attacks can also
lead to another problem, the man in the middle attack (Woodward, 2005).
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