Security Issues in Wireless Networks

Security Issues in 802.11 Wireless Networks
Prabhaker Mateti Wright State University

Talk Outline Wireless LAN Overview Wireless Network Sniffing
Wireless Spoofing Wireless Network Probing AP Weaknesses Denial of Service Man-in-the-Middle Attacks War Driving Wireless Security Best Practices Conclusion Mateti WiFi Security

Ack This talk is an overview of what has been known for a couple of years. Figures borrowed from many sources on the www. Apologies that I lost track of the original sources. Mateti WiFi Security

This talk is based on … Prabhaker Mateti, “Hacking Techniques in Wireless Networks”, in The Handbook of Information Security, Editor: Bidgoli, John Wiley, 2005 InternetSecurity/ Mateti WiFi Security

Without security issues
Wireless LAN Overview Without security issues

OSI Model Application Presentation Session Transport Network Data Link
MAC header 802.11 Physical PLCP header Mateti WiFi Security

IEEE 802.11 Published in June 1997 2.4GHz operating frequency
1 to 2 Mbps throughput Can choose between frequency hopping or direct sequence spread modulation Mateti WiFi Security

IEEE 802.11b 1999 Data Rate: 11 Mbps Reality: 5 to 7 Mbps
2.4-Ghz band; runs on 3 channels shared by cordless phones, microwave ovens, and many Bluetooth products Only direct sequence modulation is specified Most widely deployed today Mateti WiFi Security

IEEE 802.11a Data Rate: 54 Mbps Reality: 25 to 27 Mbps
Runs on 12 channels Not backward compatible with b Uses Orthogonal Frequency Division Multiplexing (OFDM) Mateti WiFi Security

IEEE 802.11g An extension to 802.11b Data rate: 54 Mbps 2.4-Ghz band
Mateti WiFi Security

Final draft expected in 2010 Data rate: 600 Mbps 2.4-Ghz band
IEEE n An extension to a/b/g Final draft expected in 2010 Data rate: 600 Mbps 2.4-Ghz band Mateti WiFi Security

802 .11 Terminology: Station (STA)
Device that contains IEEE conformant MAC and PHY interface to the wireless medium, but does not provide access to a distribution system Most often end-stations available in terminals (work-stations, laptops etc.) Typically Implemented in a PC-Card Built into recent laptops and PDAs Mateti WiFi Security

Station Architecture Ethernet-like driver interface
supports virtually all protocol stacks Frame translation according to IEEE 802.1H Ethernet Types 8137 (Novell IPX) and 80F3 (AARP) encapsulated via the Bridge Tunnel encapsulation scheme IEEE frames: translated to All other Ethernet Types: encapsulated via the RFC 1042 (Standard for the Transmission of IP Datagrams over IEEE 802 Networks) encapsulation scheme Maximum Data limited to 1500 octets Transparent bridging to Ethernet Platform Computer PC-Card Hardware Radio WMAC controller with Station Firmware (WNIC-STA) Driver Software (STADr) frame format 802.3 frame format Ethernet V2.0 / 802.3 frame format Protocol Stack Mateti WiFi Security

Radio Frequency Spectrum
GHz IEEE a HiperLAN/2 Mateti WiFi Security

Channel Spacing (5MHz) 2.462 2.437 2.412 Non-overlapping channels

Terminology: Access-Point (AP)
A transceiver that serves as the center point of a stand-alone wireless network or as the connection point between wireless and wired networks. Device that contains IEEE conformant MAC and PHY interface to the wireless medium, and provide access to a Distribution System for associated stations (i.e., AP is a STA) Most often infra-structure products that connect to wired backbones Implemented in a “box” containing a STA PC-Card. Mateti WiFi Security

Access-Point (AP) Architecture
Stations select an AP and “associate” with it APs support Roaming Power Management Time synchronization functions (Beaconing) Traffic flows through AP Bridge Software PC-Card Hardware Radio WMAC controller with Access Point Firmware (WNIC-AP) Driver (APDr) frame format 802.3 frame format Ethernet V2.0 / 802.3 frame format Kernel Software (APK) Ethernet Interface Mateti WiFi Security

Basic Configuration Mateti WiFi Security

Terminology: Basic Service Set (BSS)
A set of stations controlled by a single “Coordination Function” (that determines when a station can transmit or receive) Similar to a “cell” in pre IEEE terminology A BSS may or may not have an AP Mateti WiFi Security

Basic Service Set (BSS)

Terminology: Distribution System (DS)
A system to interconnect a set of BSSs Integrated: A single AP in a standalone network Wired: Using cable to interconnect the AP Wireless: Using wireless to interconnect the AP Mateti WiFi Security

Terminology: Independent Basic Service Set (IBSS)
A BSS forming a self-contained network in which no access to a Distribution System is available A BSS without an AP One of the stations in the IBSS can be configured to “initiate” the network and assume the Coordination Function Diameter of the cell determined by coverage distance between two wireless stations Mateti WiFi Security

Independent Basic Service Set (IBSS)

Terminology: Extended Service Set (ESS)
A set of one or more BSS interconnected by a Distribution System (DS) Traffic always flows via AP Diameter of the cell is double the coverage distance between two wireless stations Mateti WiFi Security

Terminology: Service Set Identifier (SSID)
Network name Up to 32 bytes long One network (ESS or IBSS) has one SSID E.g., “WSU Wireless”; Known Defaults for many vendors “101” for 3COM “tsunami” for Cisco Mateti WiFi Security

Terminology: Basic Service Set Identifier (BSSID)
Cell identifier One BSS has one BSSID 6 bytes long BSSID = MAC address of AP Mateti WiFi Security

Communication CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) instead of Collision Detection WLAN adapter cannot send and receive traffic at the same time on the same channel Hidden Node Problem Four-Way Handshake Mateti WiFi Security

Four-Way Handshake Source Destination RTS – Request to Send
CTS – Clear to Send DATA ACK Mateti WiFi Security

Infrastructure operation modes
Root Mode Repeater Mode Mateti WiFi Security

802.11 Packet Structure 30 byte header 4 addresses
Mateti WiFi Security Graphic Source: Network Computing Magazine August 7, 2000

802.11 Physical Layer Packet Structure
24 byte header (PLCP, Physical Layer Convergence Protocol) Always transferred at 1 Mbps Mateti WiFi Security Graphic Source: Network Computing Magazine August 7, 2000

802.11 Frames Format depends on type of frame Control Frames
Management Frames Data Frames Mateti WiFi Security

802.11 Frame Formats Bytes: 2 2 6 6 6 2 6 0-2312 4 Frame Addr 1 Addr 2
Duration Frame Control ID Addr 1 Addr 2 Addr 3 Sequence Addr 4 Body Control CRC MAC Header Bits: 2 2 4 1 1 1 1 1 1 1 1 Protocol To From More Pwr More Version Type SubType Retry WEP Rsvd DS DS Frag Mgt Data Frame Control Field Mateti WiFi Security

Address Field Description
Protocol Version Type SubType To DS Retry Pwr Mgt More Data WEP Rsvd Frame Control Field Bits: 2 2 4 1 From Frag To DS From DS Address 1 DA BSSID RA Address 2 SA TA Address 3 Address 4 N/A Addr. 1 = All stations filter on this address. Addr. 2 = Transmitter Address (TA), Identifies transmitter to address the ACK frame to. Addr. 3 = Dependent on To and From DS bits. Addr. 4 = Only needed to identify the original source of WDS (Wireless Distribution System) frames. Mateti WiFi Security

Type field descriptions
Protocol Version Type SubType To DS Retry Pwr Mgt More Data WEP Rsvd Frame Control Field Bits: 2 2 4 1 From Frag Type and subtype identify the function of the frame: Type=00 Management Frame Beacon (Re)Association Probe (De)Authentication Power Management Type=01 Control Frame RTS/CTS ACK Type=10 Data Frame Mateti WiFi Security

802.11 Management Frames Beacon Probe Probe Response
Timestamp, Beacon Interval, Capabilities, SSID, Supported Rates, parameters Traffic Indication Map Probe SSID, Capabilities, Supported Rates Probe Response Same for Beacon except for TIM Mateti WiFi Security

Management Frames (cont’d)
Association Request Capability, Listen Interval, SSID, Supported Rates Association Response Capability, Status Code, Station ID, Supported Rates Re-association Request Capability, Listen Interval, SSID, Supported Rates, Current AP Address Re-association Response Mateti WiFi Security

Management Frames (cont’d)
Dis-association Reason code Authentication Algorithm, Sequence, Status, Challenge Text De-authentication Reason Mateti WiFi Security

Association + Authentication
State 1: Unauthenticated Unassociated Successful authentication Deauthentication State 2: Authenticated Unassociated Deauthentication Successful association Disassociation State 3: Authenticated Associated Mateti WiFi Security

Authentication To control access to the infrastructure via authentication. The station first needs to be authenticated by the AP in order to join the APs network. Stations identify themselves to other stations (or APs) prior to data traffic or association. Two authentication subtypes: Open system. shared key. Mateti WiFi Security

Open System Authentication
A sends an authentication request to B B sends the result back to A Mateti WiFi Security

Shared Key Authentication

Access Point Discovery
Beacons sent out 10x second Advertise capabilities Station queries access points Requests features Access points respond With supported features Authentication just a formality May involve more frames Probe request Authentication request Association request Probe response Authentication response Association response Mateti WiFi Security

Association Next Step after authentication
Association enables data transfer between Client and AP The Client sends an association request frame to the AP who replies to the client with an association response frame either allowing or disallowing the association Mateti WiFi Security

Association To establish relationship with AP
Stations scan frequency band to and select AP with best communications quality Active Scan: send a “Probe request” on specific channels and assess response Passive Scan: assess communications quality from beacon message AP maintains list of associated stations in MAC FW Record station capability (data-rate) To allow inter-BSS relay Station’s MAC address is also maintained in bridge learn table associated with the port it is located on Mateti WiFi Security

WEP: Wired Equivalent Privacy
Designed to be computationally efficient, self-synchronizing, and exportable Data headers remain unencrypted. The cipher used is RC4(v, k) Shared key k: Manual distribution among clients. Mateti WiFi Security

WEP Encryption WEP encryption key: a shared 40- or 104-bit long number. WEP keys are used for authentication and encryption of data. A 32-bit integrity check value (ICV) is calculated that provides data integrity for the MAC frame. The ICV is appended to the end of the frame data. A 24-bit initialization vector (IV) is appended to the WEP key. IV and WEP encryption key are input to a pseudo-random number generator (PRNG) to generate a bit sequence that is the same size as the combination of [data+ICV]. The PRNG bit sequence is bit-wise XORed with [data+ICV] to produce the encrypted portion of the payload that is sent between the wireless AP and the wireless client. The IV is added to the front of the encrypted [data+ICV] which becomes the payload for the wireless MAC frame. The result is IV+ encrypted [data+ICV]. Mateti WiFi Security

WEP Decryption IV is obtained from the front of the MAC payload.
WEP encryption key is concatenated with the IV. The concatenated WEP encryption key and IV is used as the input of the same PRNG to generate a bit sequence of the same size as the combination of the [data + ICV]. The PRNG bit sequence is XORed with the encrypted [data+ICV] to decrypt the [data+ICV] portion of the payload. The ICV for the data portion of the payload is calculated and compared with the value included in the incoming frame. The WEP key remains constant over a long duration (days and months) but the IV can be changed frequently depending on the degree of security needed. Mateti WiFi Security

WEP 24 bits Append ICV = CRC32(Data) Select and insert IV
Hdr Data Append ICV = CRC32(Data) ICV Encrypted Data IV Select and insert IV Per-packet Key = IV || RC4 Base Key RC4 Encrypt Data || ICV Remove IV from packet RC4 Decrypt Data || ICV Check ICV = CRC32(Data) 24 bits Mateti WiFi Security

WEP Protocol Key is shared by all clients and the base station.
PRNG – Pseudo Random Number Gen Mateti WiFi Security

WEP .. cont Mateti WiFi Security

Drawbacks of WEP Protocol
The determination and distribution of WEP keys are not defined There is no defined mechanism to change the WEP key either per authentication or periodically for an authenticated connection No mechanism for central authentication, authorization, and accounting No per-frame authentication mechanism to identify the frame source. No per-user identification and authentication Mateti WiFi Security

Initialization Vector (IV)
Over a period, same plaintext packet should not generate same ciphertext packet IV is random, and changes per packet Generated by the device on the fly 24 bits long 64 bit encryption: IV bits WEP key 128 bit encryption: IV bits WEP key Mateti WiFi Security

WiFi Security Mateti WiFi Security

Wireless Threats Passive eavesdropping and traffic analysis
Message injection and active eavesdropping Message deletion and interception Masquerading and malicious access points Session hijacking Denial of service (DoS) Mateti WiFi Security

Network Sniffing Sniffing is eavesdropping, a reconnaissance technique
A sniffer is a program that intercepts and decodes network traffic broadcast through a medium Sniffing is the act by a machine S of making copies of a network packet sent by machine A intended to be received by machine B Sniffing is not a TCP/IP problem enabled by the media, Ethernet and , at the physical and data link layers Mateti WiFi Security

Wireless Network Sniffing
Wireless LAN sniffers can be used to gather information about the wireless network from a distance with a directional antenna RF monitor mode of a wireless card allows every frame appearing on a channel to be copied as the radio of the station tunes to various channels. Analogous to wired Ethernet card in promiscuous mode A station in monitor mode can capture packets without associating with an AP or ad-hoc network Many wireless cards permit RF monitor mode Mateti WiFi Security

Passive Scanning Eavesdropper does NOT transmit packets.
A wlan can be “listened to” outside a building using readily available technology Mateti WiFi Security

Passive Scanning A passive scanner instructs the wireless card to listen to each channel for a few messages Passive scanners are capable of gathering the passwords from the HTTP sites and the telnet sessions sent in plain text An attacker can passively scan without transmitting at all. These attacks do not leave any trace of the attacker’s presence on the network Mateti WiFi Security

Passive Scanning: Why? Scanning is a reconnaissance technique
Detection of SSID Collecting the MAC addresses Collecting the frames for cracking WEP Mateti WiFi Security

A Basic “Attack” Behind the scenes of a completely passive wireless pre-attack session using kismet

Kismet Kismet is a wireless sniffer
Setting up Kismet is fairly straightforward Google on “Kismet” for articles Mateti WiFi Security

Starting Kismet The mysqld service is started.
The gpsd service is started on serial port 1. The wireless card is placed into monitor mode. kismet is launched. Mateti WiFi Security

Detection Kismet picks up some wireless jabber! In order to take a closer look at the traffic, disengage “autofit” mode by pressing “ss” to sort by SSID. type WEP? yes or no. 4 TCP packets IP’s detected strength Mateti WiFi Security

Network Details Network details for the address are viewed by pressing the “i” key. Mateti WiFi Security

More network details More network details for the address are viewed by pressing the “i” key, then scrolling down to view more information. Mateti WiFi Security

traffic dump A dump of “printable” traffic can be had by pressing the “d” key. \MAILSLOTS? Could this be a post office computer? (that is a joke. feel free to laugh at this point. thank you.) Mateti WiFi Security

packet list A list of packet types can be viewed by selecting a wireless point and pressing “p” Mateti WiFi Security

gpsmap A map of the area is printed: # gpsmap –S2 –s10 -r gpsfile

wireshark - Beacon The *.dump files Kismet generates can be opened with tcpdump or wireshark This is an beacon frame. Mateti WiFi Security

wireshark – Probe Request
....an Probe Request from the same machine Mateti WiFi Security

wireshark - Registration
oooh... a NETBIOS registration packet for “MSHOME”... Mateti WiFi Security

wireshark - Registration
...another registration packet, this time from “LAP10”... Mateti WiFi Security

wireshark – DHCP request
...a DHCP request... it would be interesting to spoof a response to this... Mateti WiFi Security

wireshark – Browser request
...a NETBIOS browser request... Mateti WiFi Security

wireshark – Browser announce
...an SMB host announcement... revealing an OS major version of 5 and an OS minor version of 1... We have a Windows XP client laptop searching for an access point. This particular target ends up being nothing more than a lone client crying out for a wireless server to connect to. Spoofing management frames to this client would most likely prove to be pointless... Mateti WiFi Security

Passive Scanning This simple example demonstrates the ability to monitor even client machines which are not actively connected to a wireless access point. In a more “chatty” environment, so much more is possible. All of this information was captured passively. Kismet did not send a single packet on the airwaves. This type of monitoring can not be detected, but preventive measures can be taken. Mateti WiFi Security

Detection of SSID SSID occurs in the following frame types: beacon, probe requests, probe responses, association requests, and reassociation requests. Management frames are always in the clear, even when WEP is enabled. Merely collect a few frames and note the SSID. What if beacons are turned off? Or SSID is hidden? Mateti WiFi Security

When the Beacon displays a null SSID …
Patiently wait. Recall that management frames are in the clear. Wait for an associate request; Associate Request and Response both contain the SSID. Wait for a Probe Request; Probe Responses contain SSID. Mateti WiFi Security

Beacon transmission is disabled ...
Wait for a voluntary Associate Request to appear. Or Actively probe by injecting spoofed frames, and then sniff the response Mateti WiFi Security

Collecting the MAC Addresses
Attacker gathers legitimate MAC addresses for use later in spoofed frames. The source and destination MAC addresses are always in the clear in all the frames. The attacker sniffs these legitimate addresses Mateti WiFi Security

WEP Attacks Systematic procedures in cracking the WEP.
Need to collect a large number of frames. Collection may take hours to days. Time required depends heavily on saturation of access point Cracking may take a few seconds to a couple of hours. Cracking uses “weakness” in IV Four types of attacks Passive attacks to decrypt traffic based on statistical analysis Active attack to inject new traffic from unauthorized mobile stations, based on known plaintext Active attacks to decrypt traffic, based on tricking the access point Dictionary-building attack that, after analysis of about a day's worth of traffic, allows real-time automated decryption of all traffic Mateti WiFi Security

What is a “Weak” IV? Key Scheduling Algorithm (KSA) creates an IV-based on the base key A flaw in the WEP implementation of RC4 allows “weak” IVs to be generated Those IVs give away info about the bytes of the key they were derived from An attacker will collect enough weak IVs to reveal bytes of the base key Mateti WiFi Security

Initialization Vector, IV
IV is only 24 bits providing 16,777,216 different RC4 cipher streams for a given WEP key Chances of duplicate IVs are: 1% after 582 encrypted frames 10% after 1881 encrypted frames 50% after 4,823 encrypted frames 99% after 12,430 encrypted frames Increasing Key size will not make WEP any safer. Why? Walker, “IEEE i wireless LAN: Unsafe at any key size”, Oct 2000 Mateti WiFi Security

UC Berkeley Study Bit flipping Replay
Bits are flipped in WEP encrypted frames, and ICV CRC32 is recalculated Replay Bit flipped frames with known IVs re-sent AP accepts frame since CRC32 is correct Layer 3 device will reject, and send predictable response Response database built and used to derive key Mateti WiFi Security

UC Berkeley Study Stream Cipher 1234
PlainText Data Is XORed with the WEP Stream Cipher to Produce the Encrypted CipherText PlainText CipherText Cisco WEP XXYYZZ Predicted PlainText Cisco If CipherText Is XORed with Guessed PlainText, the Stream Cipher Can Be Derived CipherText Stream Cipher XXYYZZ WEP 1234 Mateti WiFi Security

UC Berkeley Study Bit Flipped Frame Sent
Frame Passes ICV Forwarded to Dest MAC Upper Layer Protocol Fails CRC Sends Predictable Error Message to Source MAC AP WEP Encrypts Response and Forwards to Source MAC Attacker Anticipates Response from Upper Layer Device and Attempts to Derive Key Mateti WiFi Security

Wireless Spoofing

Wireless Spoofing The attacker constructs frames by filling selected fields that contain addresses or identifiers with legitimate looking but non-existent values, or with legitimate values that belong to others. The attacker would have collected these legitimate values through sniffing. Mateti WiFi Security

MAC Address Spoofing Probing is sniffable by the sys admins.
Attacker wishes to be hidden. Use MAC address of a legitimate card. APs can filter based on MAC addresses. Mateti WiFi Security

IP spoofing Replacing the true IP address of the sender (or, in some cases, the destination) with a different address. Defeats IP address based trust. IP spoofing is an integral part of many attacks. Mateti WiFi Security

Frame Spoofing Frames themselves are not authenticated in 802.11.
Construction of the byte stream that constitutes a spoofed frame is facilitated by libraries. The difficulty here is not in the construction of the contents of the frame, but in getting it radiated (transmitted) by the STA or an AP. This requires control over the firmware. Mateti WiFi Security

Wireless Network Probing

Wireless Network Probing
Send cleverly constructed packets to a target that triggers useful responses. This activity is known as probing or active scanning. The target can discover that it is being probed. Mateti WiFi Security

Active Attacks Attacker can connect to an AP and obtain an IP address from the DHCP server. A business competitor can use this kind of attack to get the customer information which is confidential to an organization. Mateti WiFi Security

Detection of SSID Beacon transmission is disabled, and the attacker does not wish to wait … Inject a probe request frame using a spoofed source MAC address. The probe response frame from the APs will contain, in the clear, the SSID and other information similar to that in the beacon frames. Mateti WiFi Security

Detection of APs and stations
Certain bits in the frames identify that the frame is from an AP. If we assume that WEP is either disabled or cracked, the attacker can also gather the IP addresses of the AP and the stations. Mateti WiFi Security

Detection of Probing The frames that an attacker injects can be sniffed by a sys admin. GPS-enabled equipment can identify the physical coordinates of a transmitting device. Mateti WiFi Security

AP Weaknesses

Poorly Constructed WEP keys
The default WEP keys used are often too trivial. APs use simple techniques to convert the user’s key board input into a bit vector. Usually 5 or 13 ASCII printable characters are directly mapped by concatenating their ASCII 8-bit codes into a 40-bit or 104-bit WEP key. A stronger 104-bit key can be constructed from 26 hexadecimal digits. It is possible to form an even stronger 104 bit WEP key by truncating the MD5 hash of an arbitrary length pass phrase. Mateti WiFi Security

Defeating MAC Filtering
Typical APs permit access to only those stations with known MAC addresses. Easily defeated by the attacker Spoofs his frames with a MAC address that is registered with the AP from among the ones that he collected through sniffing. That a MAC address is registered can be detected by observing the frames from the AP to the stations Mateti WiFi Security

Rogue Networks Rogue AP = an unauthorized access point
Network users often set up rogue wireless LANs to simplify their lives Rarely implement security measures Network is vulnerable to War Driving and sniffing and you may not even know it Trojan AP = Rogue AP with malicious intent Mateti WiFi Security

Trojan AP Mechanics Create a competing wireless network.
AP can be actual AP or HostAP of Linux Create or modify captive portal behind AP Redirect users to “splash” page DoS or theft of user credentials, or … Bold attacker will visit ground zero. Not-so-bold will drive-by with an amp. So what are the mechanics behind a rogue access point? Basically, the idea is to simply create a competing wireless network. A rogue AP is essentially a wireless network of its own, but with a purpose other than providing legitimate service to the Intranet. Instead, the main purpose is to steal credentials from unsuspecting users and use those credentials for illegitimate access to the target legitimate network. The AP component of a rogue AP can be an actual access point or a simple wireless card running HostAP. Off the backend of the AP, an attacker can create a captive portal, which accepts DNS and web queries, but redirects all users to a “splash” page of some sort. Depending on how open the wireless network is to begin with, we can simply sit as a “man in the middle” acting as a “repeater” of sorts, brokering wireless connections from the rogue wireless network, to the legitimate wireless network. An attacker can simply deny service to all users or go so far as to steal usernames and passwords—perhaps even provide no interaction with the user and simply make the user a vector for some infection into the wired network. If the attacker is bold, they can do this intermittently while using the network. One day, they are a legitimate user, the next, a rogue AP—yet another new insider threat for you. A big antenna and amp can facilitate a drive-by rogue AP. Let’s see an example rogue AP setup in action. Mateti WiFi Security

Equipment Flaws Numerous flaws in equipment from well-known manufacturers Search on “access point vulnerabilities” Ex 1: Receiving a request for a file named config.img via TFTP, an AP sends its configuration. The image includes the administrator’s password required by the HTTP user interface, the WEP encryption keys, MAC address, and SSID. Ex 2: An AP returns the WEP keys, MAC filter list, administrator’s password when sent a UDP packet to port containing the string “gstsearch”. Mateti WiFi Security

Denial of Service

Denial of Service A system is not providing services to authorized clients because of resource exhaustion by unauthorized clients. DoS attacks are difficult to prevent Difficult to stop an on-going attack Victim and its clients may not even detect the attacks Duration may range from milliseconds to hours. A DoS attack against an individual station enables session hijacking Mateti WiFi Security

Jamming The hacker can use a high power RF signal generator to interfere with the ongoing wireless connection, making it useless. Can be avoided only by physically finding the jamming source. Mateti WiFi Security

Flooding with Associations
AP inserts the data supplied by the STA in the Association Request into a table called the association table specifies a maximum value of 2007 concurrent associations to an AP. The actual size of this table varies among different models of APs. When this table overflows, the AP would refuse further clients Attacker authenticates several non-existing STA using legitimate-looking but randomly generated MAC addresses. The attacker then sends a flood of spoofed associate requests so that the association table overflows Enabling MAC filtering in the AP will prevent this attack Mateti WiFi Security

Deauth/Disassoc Management frame
Attacker must spoof AP MAC address in Src Addr and BSSID Sequence Control field handled by firmware (not set by attacker) Mateti WiFi Security

Forged Dissociation Attacker sends a spoofed Disassociation frame where the source MAC address is set to that of the AP. To prevent Reassociation, the attacker continues to send Disassociation frames for a desired period. Mateti WiFi Security

Forged Deauthentication
After an Association Response frame is observed, the attacker sends a spoofed Deauthentication frame where the source MAC address is spoofed to that of the AP. The station is now unassociated and unauthenticated, and needs to reconnect. To prevent a reconnection, the attacker continues to send Deauthentication frames for a desired period. Neither MAC filtering nor WEP protection will prevent this attack Mateti WiFi Security

First Stage – Deauth Attack
Airopeek Trace of Deauth Attack Mateti WiFi Security

Decode of Deauthentication Frame Mateti WiFi Security

Power Management Power-management schemes place a system in sleep mode when no activity occurs The Client can be configured to be in continuous aware mode (CAM) or Power Save Polling (PSP) mode Mateti WiFi Security

Power Saving Attacker steals packets for a station while the station is in Doze state. The protocol requires a station to inform the AP through a successful frame exchange that it wishes to enter the Doze state from the Active state. Periodically the station awakens and sends a PS-Poll frame to the AP. The AP will transmit in response the packets that were buffered for the station while it was dozing. This polling frame can be spoofed by an attacker causing the AP to send the collected packets and flush its internal buffers. An attacker can repeat these polling messages so that when the legitimate station periodically awakens and polls, AP will inform that there are no pending packets. Mateti WiFi Security

Man-in-the-Middle Attacks

Man-in-the-Middle Attacks
Attacker on host X inserts X between all communication between hosts B and C, and neither B nor C is aware of the presence of X. All messages sent by B do reach C but via X, and vice versa. The attacker can merely observe the communication or modify it before sending it out. Mateti WiFi Security

Wireless MITM Attack A hacker uses a Trojan AP to hijack mobile nodes by sending a stronger signal than the actual AP is sending to those nodes. The clients then associates with the Trojan AP, sending its data into the wrong hands. Mateti WiFi Security

Wireless MITM Attack Assume that station B was authenticated with C, a legitimate AP. Attacker X is a laptop with two wireless cards. Through one card, he presents X as an AP. Attacker X sends Deauthentication frames to B using the C’s MAC address as the source, and the BSSID he has collected. B is deauthenticated and begins a scan for an AP and may find X on a channel different from C. There is a race condition between X and C. If B associates with X, the MITM attack succeeded. X will re-transmit the frames it receives from B to C. These frames will have a spoofed source address of B. Mateti WiFi Security

Attack machine uses vulnerabilities to get information about AP and clients. Attack machine sends deauthentication frames to victim using the AP’s MAC address as the source Mateti WiFi Security

Second Stage – Client Capture
Victim’s card scans channels to search for new AP Victim’s card associates with Trojan AP on the attack machine Attack machine’s fake AP is duplicating MAC address and ESSID of real AP Fake AP is on a different channel than the real one Mateti WiFi Security

Third Stage – Connect to AP
Attack machine associates with real AP using MAC address of the victim’s machine. Attack machine is now inserted and can pass frames through in a manner that is transparent to the upper level protocols Mateti WiFi Security

The Monkey – Jack Attack

Monkey-Jack Detection
Why do I hear my MAC Address as the Src Addr? Is this an attack? Am I being spoofed? Mateti WiFi Security

Beginning of a MITM IDS Algorithm

ARP Poisoning ARP poisoning is an attack technique that corrupts the ARP cache that the OS maintains with wrong MAC addresses for some IP addresses. ARP cache poisoning is an old problem in wired networks. ARP poisoning is one of the techniques that enables the man-in-the-middle attack. ARP poisoning on wireless networks can affect wired hosts too. Mateti WiFi Security

Session Hijacking Session hijacking occurs when an attacker causes a user to lose his connection, and the attacker assumes his identity and privileges for a period. An attacker disables temporarily the user’s system, say by a DoS attack or a buffer overflow exploit. The attacker then takes the identity of the user. The attacker now has all the access that the user has. When he is done, he stops the DoS attack, and lets the user resume. The user may not detect the interruption if the disruption lasts no more than a couple of seconds. Hijacking can be achieved by forged disassociation DoS attack. Corporate wireless networks are set up so that the user is directed to an authentication server when his station attempts a connection with an AP. After the authentication, the attacker employs the session hijacking described above using spoofed MAC addresses. Mateti WiFi Security

War Driving “The benign act of locating and logging wireless access points while in motion.” -- ( of course useful to attackers. Drive around (or walk) Possible: 10 mile range using a parabolic dish antenna. “PC cards” vary in power: 25mW mW Mateti WiFi Security

Wireless Hacking Tools

802.11 Attack Freeware Many open source also
Airsnort (Linux) WEPcrack (Linux) Kismet (Linux) Wellenreiter (Linux) NetStumbler (windows) MiniStumbler (PocketPC) BSD – Airtools (*BSD) Aerosol (Windows) WiFiScanner (Linux) BackTrack 5 Linux Penetration Tools Distro Details of a few follow Mateti WiFi Security

802.11 Network Security Tools
AiroPeek / AiroPeek NX: Wireless frame sniffer / analyzer, Windows AirTraf: Wireless sniffer / analyzer / “IDS” AirSnort: WEP key “cracker” BSD Airtools: Ports for common wireless tools, very useful Mateti WiFi Security

Airsnarf Simplifies HostAP, httpd, dhcpd, Net::DNS, and iptables setup
Simple example of a rogue AP Airsnarf is a rogue AP setup utility we will now demonstrate. Simply put, it’s just a shell script that integrates and sets up several fairly standard Linux utilities to create a rogue access point, specifically: HostAP for AP functionality, httpd to serve up the splash page, dhcpd to give out IPs/DNS/gateway, a simple Perl-based Net::DNS::Nameserver DNS redirect, and iptables to funnel all the DNS requests the gateway sees to a local port All of these Linux utilities are publicly available. (Demonstration) Mateti WiFi Security

Ettercap Ettercap is a suite for man in the middle attacks on LAN. It features sniffing of live connections, content filtering on the fly and many other interesting tricks. It supports active and passive dissection of many protocols (even ciphered ones) and includes many feature for network and host analysis. Mateti WiFi Security

libradiate Radiate is a C library similar in practice to Libnet but designed for " frame reading, creation and injection." Libnet builds layer 3 and above Libradiate builds frames Disperse, an example tool built using libradiate, is fully functional Mateti WiFi Security

libradiate Radiate allows construction of these frames very easily.
Frame types and subtypes Beacon transmitted often announcing a WLAN Probe request: A client frame- "anyone out there?" Association: client and server exchange- "can i play?" Disassociate: "no soup for you!" RTS/CTS: ready/clear to send frames ACK: Acknowlegement Radiate allows construction of these frames very easily. Mateti WiFi Security

netstumbler Access point enumeration tool, Windows, free
Supports GPS but lacks features required by a real wireless security hacker... Mateti WiFi Security

stumbverter (2002) thanks to fr|tz @ www.mindthief.net for map data!

Wireless Geographic Logging Engine: Making maps of wireless networks since 2001 45 Million Wifi Networks! Sep 27, 2011 Download Wigle Wifi for Android Download the JiGLE Java Client Download the DiGLE Windows Native client Mateti WiFi Security

kismet: wireless network sniffer
Segregates traffic Detects IP blocks decloaks SSID’s Detects factory default configurations Detects netstumbler clients Maps wireless points Mateti WiFi Security

air-jack A family of tools based on the air-jack driver
wlan-jack: spoofs a deauthentication frame to force a wireless user off the net essid-jack: wlan-jacks a victim then sniffs the SSID when the user reconnects Monkey-jack: wlan-jacks a victim, then plays man-in-the-middle between the attacker and the target kracker-jack: monkey-jacks a WLAN connection Mateti WiFi Security

Wireless Security Best Practices

Location of the APs Network segmentation RF signal shaping
Treat the WLAN as an untrusted network RF signal shaping Continually check for unauthorized (“rogue/Trojan”) APs Mateti WiFi Security

Proper Configuration Change the default passwords
Use WEP, however broken it may be Don't use static keys, change them frequently Don't allow connections with an empty SSID Don't broadcast your SSID Use a VPN and MAC address filtering with strong mutual authentication Wireless IDS/monitoring (e.g., Mateti WiFi Security

Proper Configuration Most devices have multiple management interfaces
HTTP Telnet FTP TFTP SNMP Disable unneeded services / interfaces Stay current with patches Mateti WiFi Security

Remedies Secure Protocol Techniques Use strong authentication
Encrypted messages Digitally signed messages Encapsulation/tunneling Use strong authentication Mateti WiFi Security

Wireless IDS A wireless intrusion detection system (WIDS) is often a self-contained computer system with specialized hardware and software to detect anomalous behavior. The special wireless hardware is more capable than the commodity wireless card, including the RF monitor mode, detection of interference, and keeping track of signal-to-noise ratios. It also includes GPS equipment so that rogue clients and APs can be located. A WIDS includes one or more listening devices that collect MAC addresses, SSIDs, features enabled on the stations, transmit speeds, current channel, encryption status, beacon interval, etc. Mateti WiFi Security

Wireless IDS WIDS computing engine should be powerful enough that it can dissect frames and WEP-decrypt into IP and TCP components. These can be fed into TCP/IP related intrusion detection systems. Unknown MAC addresses are detected by maintaining a registry of MAC addresses of known stations and APs. Can detect spoofed known MAC addresses because the attacker could not control the firmware of the wireless card to insert the appropriate sequence numbers into the frame. Mateti WiFi Security

Wireless Auditing Periodically, every wireless network should be audited. Several audit firms provide this service for a fee. A security audit begins with a well-established security policy. A policy for wireless networks should include a description of the geographical volume of coverage. The goal of an audit is to verify that there are no violations of the policy. Mateti WiFi Security

IEEE 802.1X General-purpose port based network access control mechanism for 802 technologies Authentication is mutual, both the user (not the station) and the AP authenticate to each other. supplicant - entity that needs to be authenticated before the LAN access is permitted (e.g., station); authenticator - entity that supports the actual authentication (e.g., the AP); authentication server - entity that provides the authentication service to the authenticator (usually a RADIUS server). Extensible Authentication Protocol (EAP) RFC 2284) that was first developed in the Internet community for Point-to-Point Protocol (PPP ) Authentication is mutual, both the user (not the wireless device as in the case of WEP) and the access point authenticate to each other. Prevents rogue access points EAP in 802.1x is called EAPOL (Extensible Authentication Protocol over LANs) and is based on three entities: supplicant - entity that needs to be authenticated before the LAN access is permitted (i.e. the wireless client station); authenticator - entity that supports the actual authentication (i.e. the access point); authentication server - entity that provides the authentication service to the authenticator (usually a RADIUS server). Mateti WiFi Security

IEEE 802.1X Extensible Authentication Protocol (EAP)
Can provide dynamic encryption key exchange, eliminating some of the issues with WEP Roaming is transparent to the end user Microsoft includes support in Windows Mateti WiFi Security

802.1x Architecture Mateti WiFi Security

Cisco LEAP Overview Provides centralized, scalable, user-based authentication Algorithm requires mutual authentication Network authenticates client, client authenticates network Uses 802.1X for authentication messaging APs will support WinXP’s EAP-TLS also Dynamic WEP key support with WEP key session timeouts Mateti WiFi Security

LEAP Authentication Process
Client AP RADIUS Server Start AP Blocks All Requests Until Authentication Completes Request Identity Identity Identity RADIUS Server Authenticates Client Client Authenticates RADIUS Server Derive Derive Key Key Broadcast Key AP Sends Client Broadcast Key, Encrypted with Session Key Key Length Mateti WiFi Security

IEEE i Ratified: 2004 Replaces broken WEP and stopgap measures such as WPA Mutual authentication EAP-TLS/802.1X/RADIUS Data confidentiality and integrity CCMP (special mode of AES) replaces TKIP Key management protocols Discovery and Negotiation Coordination with Authentication Mateti WiFi Security

802.11i Takes base 802.1X and adds several features
Wireless implementations are divided into two groups: legacy and new Both groups use 802.1x for credential verification, but the encryption method differs Legacy networks must use 104-bit WEP, TKIP and MIC New networks will be same as legacy, except that they must replace WEP/TKIP with advanced encryption standard – operation cipher block (AES-OCB) Mateti WiFi Security

Authenticator/Supplicant Station Management Entity
802.11i Architecture Data 802.1X Authenticator/Supplicant 802.1X Controlled Port 802.1X Uncontrolled Port MAC_SAP Data Link LAYER TK 802.11i State Machines WEP/TKIP/CCMP MAC PTK  PRF(PMK) (PTK = KCK | KEK | TK) Physical Station Management Entity PHY LAYER PMD Mateti WiFi Security

Wi-Fi Protected Access (WPA)
2003 Security solution based on IEEE standards Replacement for WEP Designed to run on existing hardware as a software upgrade, Wi-Fi Protected Access is derived from and expected to be compatible with the IEEE i standard TKIP (Temporal Key Integrity Protocol) User authentication via 802.1x and EAP Mateti WiFi Security

WPA2 2004 All of WPA Support for CCMP (Counter Mode with Cipher Block Chaining Message Authentication Code Protocol) based on AES cipher as an alternative to TKIP Mateti WiFi Security

Temporal Key Integrity Protocol (TKIP)
128-bit shared secret – “temporal key” (TK) Mixes the transmitter's MAC address with TK to produce a Phase 1 key. The Phase 1 key is mixed with an initialization vector (iv) to derive per-packet keys. Each key is used with RC4 to encrypt one and only one data packet. Defeats the attacks based on “Weaknesses in the key scheduling algorithm of RC4” by Fluhrer, Mantin and Shamir" TKIP is backward compatible with current APs and wireless NICs Mateti WiFi Security

Message Integrity Check (MIC)
MIC prevents bit-flip attacks Implemented on both the access point and all associated client devices, MIC adds a few bytes to each packet to make the packets tamper-proof. Mateti WiFi Security

References Jon Edney and William A. Arbaugh, Real Security: Wi-Fi Protected Access and i, 480 pages, Addison Wesley, 2003, ISBN: Matthew S. Gast, Wireless Networks: The Definitive Guide, 464 pages, O’Reilly & Associates, April 2002, ISBN: Changhua He, "Analysis Of Security Protocols For Wireless Networks",PhD dissertation, Stanford University, December 2005 Chris Hurley, Michael Puchol, Russ Rogers, and Frank Thornton, WarDriving: Drive, Detect, Defend, A Guide to Wireless Security, ISBN: , Syngress, 2004 IEEE, IEEE standards documents, Tom Karygiannis and Les Owens, Wireless Network Security: , Bluetooth and Handheld Devices, National Institute of Standards and Technology Special Publication , November nistpubs/800-48/NIST_SP_ pdf Prabhaker Mateti, TCP/IP Suite, The Internet Encyclopedia, Hossein Bidgoli (Editor), John Wiley 2003, ISBN Prabhaker Mateti, ``Hacking Techniques in Wireless Networks'', in The Handbook of Information Security, edited by Bidgoli, John Wiley, 2005 Bruce Potter and Bob Fleck, Security, O'Reilly & Associates, 2002; ISBN: Joshua Wright, Understanding the WPA/WPA2 Break, Mateti WiFi Security

Security Issues in Wireless Networks

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