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Unformatted text preview: PASSIVE & ACTIVE ATTACKS AGAINST WIRELESS LAN’S
Mohteshim Hussain, email@example.com,
University of Hertfordshire, England, U.K. Overview of WLAN and its vulnerabilities
Wireless LAN’s (WLAN) are LAN’s networked wirelessly
using the air interface as the medium of the network. The
wireless technology being used is nothing but radio
frequency waves. WLAN can run on three different physical
media, two based on the spread spectrum and one on
diffused infrared. [Peterson & Davie, 2003- P.132].
The fact that wireless networks make use of the air interface
as the medium of the network ma kes them susceptible to
threats by attackers. Attacks are carried out with various
attacker objectives [Sankar et. al. , 2005 - P.126]. E.g. an
attacker just might want to check the network traffic, or
might want to access resources on the network.
An attack is any action carried out to compromise the
security of any information belonging to a organization.
[Stallings, 2003 – P. 4]. Furthermore Stallings classifies two
types of attacks; Active and Passive attacks. Passive attacks
are those in which the attacker obtains information being
transmitted / received by the network, these types of attacks
are usually difficult to detect as there is no modification of
the contents by the attacker. Whereas active attacks involve
the attacker changing the information / content or even
sometimes generating fraudulent information into the
network. These types of attacks are malicious in nature and
can result in severe losses for the victims [Stallings , 2003 –
P.11, Prasad, 2005 – P. 96].
The following figure represents a general classification of
attacks according to Stallings.
Modification of message
Denial of Service Passive Attacks
Release of msg.contents Fig1. Taxonomy of Active and Passive attacks
Wired Equivalent privacy (WEP) is a security algorithm
employed by WLAN’s, the main goal of WEP is not to
secure the network but completely secure the data so that the
attackers do not have access to the information and if they
do, it will be secured with the WEP algorithm. The notion of
WEP is important as in many of the attacks on WLAN
which I am going to describe; the WEP algorithm’s
vulnerability is exploited and broken. More material on
attacks on WEP algorithms can be found in “Hacking
Exposed” [McClure et. al., 2003 – P.471].
Coming towards more specific attacks on wireless networks.
One of the conference papers of The International Association
Of Science And Technology For Development – IASTED
titled “Wireless LAN Attacks And Protection Tools” gives a
very good taxonomy of active and passive attacks on
WLAN’s, whereas the amount of information provided in this paper is quite brief. The taxonomy of the attacks on a WLAN is
as follows. [IASTED, 2004].
Attacks on WLANs
Rogue Access Points
Man in the Middle Attack (MITM)
Denial of Service Passive Attacks
Passive Eavesdropping Fig2. Taxonomy of Active and Passive attacks on WLAN
1.Passive Attacks On WLAN
There are two types of passive attacks an attacker can mount:
a. Traffic Analysis
b. Passive Eavesdropping
1a. Traffic Analysis
The first step to any type of hacking is footprinting [McClure et.
al., 2003 – Chp. 1], and wireless footprinting is done by carrying
out traffic analysis. The attackers before mounting an active
attack have to obtain sufficient information about the network.
This operation of traffic analysis gives the atta cker some basic
information about the network, like, the network activity going
on, the protocols being used by the network and also the active
access points (AP’s) of the network.
The determination of the active AP’s is employed by a process
known as Wardriving [IASTED, 2004]. This is a process
where the attacker physically moves around (usually in a car
and hence the name wardriving is derived) to find out about
the active AP’s of the network to be attacked. By finding out
about the active AP the attacker can use the AP as a starting
point to mount his/her attack. This is done by detecting and
capturing the beacon frames sent out Periodically by the AP’s.
[IASTED, 2004, Sankar et. al., 2005 - P.133].
1b. Passive Eavesdropping
This attack is very similar to the traffic analysis attack
[IASTED, 2004], as this also discloses the information about
the network but at the same time the attacker can access and
read the message contents. If the Message is encrypted, this
will require the attacker to break the encryption and read the
The attacker can mainly gain two types of information by
mounting this sort of an attack; he/she can read the data
transmitted in the session and also get various information
about the packet characteristics. Therefore the impact of
passive eavesdropping is the compromise of information and
privacy [Welch – June 2003]. 2. Active Attacks on WLAN
The several types of active attacks an attacker can mount
against WLAN are:
a. Unauthorized Access
b. R ogue Access Points
c. Man In the Midd le Attack (MITM)
d. Session Hijacking
f. Denial of Service
The attack is not aimed at a particular user, but by doing
this, the attacker gains unauthorized access to the whole
network. This attack in turn gives rise to more malicious
attacks such as MITM, ARP poisoning.
In some security architectures when the attacker accesses the
wireless network, he/she also gets access to the wired
components of the network. Where as in other security
architectures the wired components are contro lled by access
control, usually implemented using ACL’s (Access Control
Lists). However the access control rights can be bypassed by
spoofing the victim’s MAC address [IASTED, 2004].
Spoofing is the same as Masquerading. The main motive of
the attack is to give the attacker the access to services or
privileges he/she is not authorized to access [Prasad, 2005 –
These can be thought of as sub divisions of the AP’s. Rogue
AP’s are setup by the users for their convenience [IASTED,
2004, Sankar et. al., 2005 - P.154]. E.g. an AP is not in the
range of the user’s current position; the user will setup a rogue
AP for the purpose of boosting the range and getting the AP’s
signal unto him.The rogue AP has no or minimal security, due
to this it becomes a very massive back door for attackers.
Even if the ro gue AP’s are secured using for example WEP,
an attacker can attack and exploit the WEP algorithm using
various methods [McClure et. al., 2003 – P.471].
An Attacker can setup a rogue AP to gain future access to
the network or even to obtain user a/c information. Some
AP’s serve as public gateways like hotspots, etc. An attacker
can set up a fraudulent rogue AP for the respective AP and
then mirror the AP’s registration page to get hold of
people’s user name and password. Rogue AP’s play and
essential part in mounting a MITM attack. [Sankar et. al.,
2005 - P.154].
2.c Man In The Middle Attacks (MITM)
These attacks have an indirect Perspective of attacking data
confidentiality. Although the organiza tions might have
employed security measures such as VPN or IPSec. These
countermeasures only protect from a direct data
confidentiality attack. This attack comprises the integrity of
messages as they can be read and/or modified by the
attacker. The attacker appears to the AP as the user and to
the user as the authentic AP, Hence this fools both the AP
and the user and all data is passed through the Attacker
[Welch – June 2003]. Masquerading/spoofing is the
technique employed by the attacker to fool the participants
of the connection. [IASTED, 2004]. 2d. Session Hijacking
This attack is also attacking the victim indirectly as the MITM
attack. Session High jacking involves taking control of the
session. The attacker will take control of the session and the
victim will think that the session is no longer in operation
whatever the cause. Whereas the session will be live and in the
hands of the attacker, which he/she can exploit for many
purposes. Session hijacking is basically done by obtaining MAC
of the AP and the victim, after the victim is authenticated by the
AP the attacker impersonates as the AP by using its MAC and
sends a MAC-Disassociate message to the victim. The victim
then closes the session but the real AP has the session open, and
the attacker then acts as the victim by using its MAC and gain s
control over the session. This attack happens in real time and
also compromises the integrity aspect. Further information in
[Welch – June 2003, IASTED, 2004].
A replay attack has the same objectives as the MITM and the
session hijacking, but this attack happens offline, rather than in
real time. The attacker can capture data of a session and can use
it later to exploit the victim’s information [IASTED, 2004]. The
information can be the user’s session information, which could
be the authentication information. Therefore by introducing
timeouts in a message, replay attacks could be avoided.
2f.Denial of Service (DoS)
This works well on WLAN and is one of the very famous
attacks, to bring down the system. The main aim is to bring
down the system so that it doesn’t respond to the users request.
This can be done by sending huge traffic at the AP, making it
unable to respond [IASTED, 2004].Hence this attack deals with
the attacker trying to keep the use r from accessing the
information or the resources of the system. The DoS attacks in
case of wireless technologies can be carried out just by
introducing interference in the form of noise, whereas flooding
packets performs a DoS attack on the network.
The attacks which I have described above are quite brief and
further information can be obtained by following up the
references. The attacks have countermeasures to them which are
not covered in this paper . Cryptographic techniques are
sometimes employed to protect against some of the attacks.
Although this particular taxonomy used in this paper is not a set
standard, but it can be used as a starting point for a WLAN
network designer. He/she can analyse these and understand the
risks involved and hence implement a wireless network which
can counter the active and passive attacks against the WLAN. References
1. IASTED (2004)
International Association of Science and Technology for Development
Document link: http://www.iasted.com/conferences/2004/banff/WNET-Hunt3b.pdf 2. McClure, S. Scambray, J. and Kurtz, G. (2003)
Hacking Exposed: Network Security secrets and solutions (4 th Edition)
McGraw Hill: NY, U.S.A. 3. Peterson, Larry L. and Davie, Bruce S (2003).
Computer Networks: A Systems Approach (3rd Edition)
Morgan Kaufmann Publishers: CA, U.S.A. 4. Prasad, A.R. and Prasad, N.R. (2005)
802.11 WLANs and IP Networking: security, QoS, and mobility
Artech House Universal Personal Communication: Boston, London 5. Sankar, K. Sundaralingam, S. Nalinsky, A. and Miller, D. (2005)
Cisco wireless LAN security:Expert guidance for securing your 802.11 networks
Cisco Press: U.S.A. 6. Stallings, W. (2003)
Cryptography and Network Security: Principles and practices (3rd Edition)
Prentice Hall: New Jersey, U.S.A. 7. Welch, D. and Lathrop, S. (2003)
Wireless Security Threat Taxonomy
Proceedings of the 2003 IEEE workshop on information assurance United States Military
Academy West Point, NY, June 2003 ...
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This note was uploaded on 02/16/2011 for the course ICT 2 taught by Professor 2 during the Spring '11 term at Kungliga Tekniska högskolan.
- Spring '11