CWAP-404 Practice Exam Questions with Answers Certified Wireless Analysis Professional Certification

 The GTK (Group Temporal Key) is encrypted within the third message of the 4-Way Handshake. The 4-Way Handshake is a process that establishes a secure connection between a STA (station) and an AP (access point) using WPA2 (Wi-Fi Protected Access 2), which is a security protocol that uses AES-CCMP (Advanced Encryption Standard-Counter Mode CBC-MAC Protocol) as its encryption algorithm. The 4-Way Handshake consists of four messages that are exchanged between the STA and the AP. The first message is sent by the AP to the STA, containing the ANonce (Authenticator Nonce), which is a random number generated by the AP. The second message is sent by the STA to the AP, containing the SNonce (Supplicant Nonce), which is a random number generated by the STA, and the MIC (Message Integrity Code), which is a value that verifies the integrity of the message. The third message is sent by the AP to the STA, containing the GTK, which is a key that is used to encrypt and decrypt multicast and broadcast data frames, and the MIC. The GTK is encrypted with the KEK (Key Encryption Key), which is derived from the PTK (Pairwise Temporal Key). The PTK is a key that is used to encrypt and decrypt unicast data frames, and it is derived from the PMK (Pairwise Master Key), the ANonce, and the SNonce. The fourth message is sent by the STA to the AP, containing only the MIC, to confirm the completion of the 4-Way Handshake. The other options are not correct, asthey are not encrypted within the third message of the 4-Way Handshake. The PMK is a key that is derived from a passphrase or obtained from an authentication server, and it is not transmitted in any message of the 4-Way Handshake. The PTK is a key that is derived from the PMK, the ANonce, and the SNonce, and it is not transmitted in any message of the 4-Way Handshake. The GMK (Group Master Key) is a key that is generated by the AP and used to derive the GTK, and it is not transmitted in any message of the 4-Way Handshake. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 8: Security Analysis, page 211-213

The channel number is not transmitted in an HT PPDU header. An HT PPDU header is a part of the PPDU that contains information such as modulation, coding, data rate, and number of spatial streams for an 802.11n transmission. The channel number is not included in the HT PPDU header, as it is determined by the frequency band and channel width that are used by the transmitter and receiver. The channel number can be inferred from the frequency band and channel width, which are indicated by bits in different fields of the HT PPDU header, such as HT-SIG and HT-LTF. The other options are not correct, as they are transmitted in an HT PPDU header. The number of spatial streams, PPDU length, and MCS index are indicated by bits in the HT-SIG field of the HT PPDU header. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 108-109

The device finder is a common feature of a spectrum analyzer that helps locate a non-802.11 interference source. The device finder uses a directional antenna to measure the signal strength of a specific frequency or signal source. By pointing the antenna in different directions, the device finder can indicate the direction and distance of the interference source. The device finder can also filter out other signals that are not related to the interference source. The other options are not correct, as they do not help locate a non-802.11 interference source. Max hold and min hold are features that show the maximum and minimum RF power levels over time,respectively. Location filter is a feature that filters out signals that are not from a specific location or area. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 3: Spectrum Analysis, page 77-78

One way to confirm if you have missing packets in your packet capture is to look for gaps in the sequence number in MAC headers. The sequence number is a 12-bit field in the MAC header that is used to identify and order data frames within a traffic stream. The sequence number is incremented by one for each new data frame transmitted by a STA, except for retransmissions, fragments, and control frames. The sequence number can range from 0 to 4095, and then wraps around to 0. If you see a jump or a gap in the sequence number between two consecutive data frames from the same STA, it means that you have missed some packets in between. The other options are not correct, as they do not confirm if you have missing packets in your packet capture. CRC errored packets are packets that have been corrupted during transmission and have failed the error detection check. Protocol analyzers may show the number of CRC errored packets in their statistics view, but not the number of missing packets. Retransmissions are an indication of packet loss or collision, but not necessarily of missing packets in your capture. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 114-115

 When performing protocol analysis, you would look at the HT Information Element in the Beacon frame to determine which one of the four HT protection modes the AP is operating in. The HT Information Element contains various subfields that provide information about the HT network configuration and operation. One of these subfields is the HT Protection field, which indicates whether any protection mechanisms are required for mixed-mode operation with non-HT STAs. The four possible values for this field are:

• No Protection: No protection mechanisms are required.
• Non-member Protection: RTS/CTS or CTS-to-self protection is required for all HT transmissions.
• 20 MHz Protection: RTS/CTS or CTS-to-self protection is required for all HT transmissions using a 40 MHz channel.
• Non-HT Mixed Mode: All HT transmissions must use a non-HT preamble and header . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 11: 802.11n/ac/ax PHYsical Layer Frame Exchanges, page 378; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 11: 802.11n/ac/ax PHYsical Layer Frame Exchanges, page 379.

The STA is discovering a list of available BSSs by sending a Probe Request with an empty SSID element. This is also known as a broadcast Probe Request, as it does not specify any particular SSID to probe for. Any AP that receives this Probe Request will respond with a Probe Response containing its own SSID and other information about its BSS. This way, the STA can learn about all the BSSs in its vicinity and choose which one to associate with . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 191; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 193.

Before a retransmission, the CWmax (Contention Window maximum) value doubles and increases by 1. The CWmax is a parameter that determines the upper limit of the random backoff time that a STA (station) has to wait before attempting to access the medium. The random backoff time is chosen from a range of values between CWmin (Contention Window minimum) and CWmax. The CWmin and CWmax values depend on the AC (Access Category) of the traffic and the PHY type of the STA. If a transmission fails due to a collision or an error, the STA has to retransmit the frame after waiting for another random backoff time. However, to reduce the probability of another collision, the STA increases its CWmax value by doubling it and adding 1. This increases the range of possible backoff values and spreads out the STAs more evenly. The STA resets its CWmax value to its original value after a successful transmission or after reaching a predefined limit. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 7: QoS Analysis, page 196-197

The interframe space that would be expected between a CTS (Clear to Send) and a Data frame is SIFS (Short Interframe Space). A SIFS is the shortest interframe space that is used for high-priority transmissions, such as ACKs (Acknowledgements), CTSs, or data frames that are part of a fragmentation or aggregation process. A SIFS is a fixed value that depends on the PHY type and channel width. A CTS and a Data frame are part of a virtual carrier sense mechanism called RTS/CTS (Request to Send/Clear to Send), which is used to avoid collisions and hidden node problems in wireless transmissions. When a STA (station) wants to send a data frame, it first sends an RTS frame to the intended receiver, indicating the duration of the transmission. The receiver then responds with a CTS frame, also indicating the duration of the transmission. The other STAs in the vicinity hear either the RTS or the CTS frame and update their NAV (Network Allocation Vector) timers accordingly, deferring their access to the medium until the transmission is over. The sender then sends the data frame after waiting for a SIFS, followed by an ACK frame from the receiver after another SIFS. The other options are not correct, as they are not used between a CTS and a Data frame. A PIFS (PCF Interframe Space) is used for medium access by the PCF (Point Coordination Function), which is an optional and rarely implemented polling-based mechanism that provides contention-free service for time-sensitive traffic. An AIFS (Arbitration Interframe Space) is used for medium access by different ACs (Access Categories), which are logical queues that correspond to different QoS (Quality of Service) levels for different types of traffic. An AIFS is a variable interframe space that depends on the AIFSN (Arbitration Interframe Space Number) value of each AC. A DIFS (Distributed Interframe Space) is used for medium access by the DCF (Distributed Coordination Function), which is the default and mandatory contention-based mechanism that provides best-effort service for normal traffic. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 6: 802.11 Frame Exchanges, page 166-167; Chapter 7: QoS Analysis, page 194-195

Receive sensitivity is the minimum signal level that a receiver can detect and decode. Different devices may have different receive sensitivity levels depending on their hardware specifications and antenna configurations. In this scenario, the portable analyzer has a lower receive sensitivity than the AP, meaning that it requires a stronger signal to capture the packets from the client STA. The AP, on the other hand, has a higher receive sensitivity and can receive the packets from the client STA even if they have a weaker signal. This explains why the portable analyzer can only see unidirectional traffic from the AP to the client when capturing near the AP5 References:

• CWAP-403 Study Guide, Chapter 4: PHY Layer Analysis, page 121
• CWAP-403 Objectives, Section 4.3: Analyze PHY layer metrics

All data frames will be retransmitted in this scenario. This is because the AP uses a Block Ack (BA) mechanism to acknowledge the receipt of multiple data frames from a client in a single frame. The BA contains a bitmap that indicates which data frames were received correctly and which were not. If the BA is not received by the AP due to frame corruption, the AP will assume that none of the data frames were received by the client and will retransmit all of them. The other options are not correct, as they do not account for the loss of the BA or the use of the bitmap. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 6: 802.11 Frame Exchanges, page 167-168

The first step in any troubleshooting process is to define the problem. This involves gathering information from various sources, such as users, network administrators, network documentation, and network monitoring tools. Defining the problem helps to narrow down the scope of the issue and identify the symptoms, causes, and effects of the problem12 References:

• CWAP-403 Study Guide, Chapter 1: Troubleshooting Methodology, page 7
• CWAP-403 Objectives, Section 1.1: Define the problem

The statement that the Frame Control field contains subfields, and some 1-bit flags is true. The Frame Control field is a 2-byte field in the MAC header that contains information about the type, subtype, and characteristics of a frame. The Frame Control field is divided into several subfields, each with a specific function and length. Some of these subfields are 1-bit flags, which can be set to 0 or 1 to indicate a certain condition or status. For example, the To DS and From DS subfields are 1-bit flags that indicate whether a frame is destined for or originated from the DS (Distribution System). The other statements are not true, as they do not describe the Frame Control field correctly. All types of frames (management, control, and data) have a Frame Control field, not just control frames. The Frame Control field is not used to communicate the duration value, which is a separate field in the MAC header. The Frame Control field is not always set to 0, as it varies depending on the type, subtype, and characteristics of each frame. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 113-114

A capture visualization tool is a software application that can open a packet capture file and display various graphs, charts, tables, and statistics that illustrate the characteristics and behavior of the wireless network. A capture visualization tool can help a network administrator with little knowledge of 802.11 protocols to evaluate the overall health and performance of their wireless network by providing a visual and intuitive representation of the captured data. A spectrum analyzer is a hardware device that measures the radio frequency signals in a given frequency range and displays their amplitude, frequency, and modulation. A spectrum analyzer can help identify sources of interference and noise in the wireless environment, but it cannot open a packet capture file. Python is a programming language that can be used to write scripts or applications that manipulate or analyze packet capture files, but it requires coding skills and knowledge of 802.11 protocols. A WLAN scanner is a software application that scans for available wireless networks and displays information such as SSID, BSSID, channel, signal strength, security type, and vendor. A WLAN scanner can help discover wireless networks and their basic parameters, but it cannot open a packet capture file345 References:

• CWAP-404 Study Guide, Chapter 2: Protocol Analysis, page 63
• CWAP-404 Objectives, Section 2.5: Use capture visualization tools
• CWAP-404 Study Guide, Chapter 4: Spectrum Analysis and Troubleshooting, page 117
• CWAP-404 Objectives, Section 4.1: Use spectrum analysis tools
• CWAP-404 Study Guide, Chapter 2: Protocol Analysis, page 33
• CWAP-404 Objectives, Section 2.2: Analyze field values