Exam PT0-002 topic 1 question 170 discussion

The ‐sA flag is used to conduct a TCP ACK scan and is most frequently used to test firewall rulesets.

B. nmap -sS 192.168.0.1/24 Explanation: -sS option is used to perform a SYN scan, which is a stealthy scan that is less likely to be detected by a firewall. By sending a SYN packet to a target and watching for a SYN-ACK or RST packet in response, the assessor can determine whether a port is open or closed. As a stateful firewall will keep track of the connection by inspecting the SYN-ACK packet and either allowing or denying the connection, the assessor can infer the firewall rule set from the scan results. Option A is a TCP ACK scan, which can be used to determine whether a firewall is in place or not, but it won't map the firewall rule set. Option C is a grepable output format, it doesn't specify any type of scan. Option D is a basic command which doesn't specify any type of scan, it will perform a default ping scan.

https://nmap.org/book/scan-methods-ack-scan.html ACK scan is used for firewall ruleset mapping.

Cert master learn says that -sS is the default and most popular option, which is what the question is asking. Topic 8a: Evade detection: Flying under the radar.

A. nmap -sA This is fundamental pentesting 101. GhatGPT is hot garbage. Go use some tools.

Read the nmap man page

The ACK scan is specifically useful for analyzing how a stateful firewall is configured in terms of how it treats packets that appear to be part of an existing connection.

From nmap: As described in depth in the section called “TCP ACK Scan (-sA)”, the ACK scan sends TCP packets with only the ACK bit set. Whether ports are open or closed, the target is required by RFC 793 to respond with a RST packet. Firewalls that block the probe, on the other hand, usually make no response or send back an ICMP destination unreachable error. This distinction allows Nmap to report whether the ACK packets are being filtered.

"ACK Scan As described in depth in the section called “TCP ACK Scan (-sA)”, the ACK scan sends TCP packets with only the ACK bit set. Whether ports are open or closed, the target is required by RFC 793 to respond with a RST packet. Firewalls that block the probe, on the other hand, usually make no response or send back an ICMP destination unreachable error. This distinction allows Nmap to report whether the ACK packets are being filtered." https://nmap.org/book/determining-firewall-rules.html

When the goal is to map out a stateful firewall rule set, the assessor is likely looking to identify how the firewall responds to different flags in the TCP header. A stateful firewall keeps track of the state of active connections, so understanding its rules requires the use of specific scanning techniques. The command that MOST likely fits this scenario is: A. nmap -sA 192.168.0.1/24 Explanation: -sA: This is the TCP ACK scan option in Nmap. It can be used to map out firewall rule sets, as stateful firewalls may react differently to packets with the ACK flag set. This type of scan can help to understand how the firewall is configured with regards to established connections. The other options are not as suited for mapping a stateful firewall:

The best option for the assessor to run in order to map out a stateful firewall rule set would be: A. nmap -sA 192.168.0.1/24 The -sA option in Nmap performs a TCP ACK scan, which can be used to determine if a firewall is stateful or not. A stateful firewall keeps track of the state of connections passing through it and can prevent certain types of attacks, such as TCP SYN floods. By sending an ACK packet to a closed port on a target system, the firewall should respond with a reset (RST) packet if it is stateful, indicating that the port is closed. If the firewall is not stateful, it will not respond to the ACK packet. This can help the assessor determine the firewall rule set and potentially identify any weaknesses in the firewall configuration.

No one said anything about being stealthy and using a SYN scan From the Nmap website: "CP ACK Scan (-sA) This scan is different than the others discussed so far in that it never determines open (or even open|filtered) ports. It is used to map out firewall rulesets, determining whether they are stateful or not and which ports are filtered."

There is no need for discussion. It is clear from the NMAP site. Don't just copy the results, READ. It is A !!!! https://nmap.org/book/scan-methods-ack-scan.html

B is the right answer

Option B ("-sS") is the most likely scan to be used for mapping out a stateful firewall rule set because it performs a TCP SYN scan. A TCP SYN scan works by sending a SYN packet to the target host, and if the port is open, the host responds with a SYN-ACK packet. However, if the port is closed, the host responds with a RST packet. By analyzing the responses from the target host, the assessor can determine which ports are open, closed, or filtered by the firewall. Option A ("-sA") is a TCP ACK scan, which is used to determine if a port is filtered or unfiltered. It sends an ACK packet to the target host, and if the port is unfiltered, the host will respond with a RST packet. If the port is filtered, the host will not respond at all. While an ACK scan can provide some information about the firewall, it is not as effective as a SYN scan for mapping out the stateful firewall rule set.

A - What is stateful firewall (One that keeps state of traffic or packet leaving the internal network to the outside and its return). A TCP Ack scan -sA fools the firewall not to know where the traffic is from and who initiated the traffic. It makes the firewall believe that a SYN-ACK from the inside is sent out and the Ack probe sent is the response to the SYN-ACK. This makes the firewall respond to states if the target is reachable with open services running.

A is the answer. https://nmap.org/book/scan-methods-ack-scan.html