Analyze Network Structure and Security
Assignments:
1. Analyze Network
2. Network Traffic Analysis
3. OS Hardening Techniques
4. Analyze Network Attack
5. Network Hardening
6. Risk Assessment Report
7. NIST Cybersecurity Framework
Assignments:
1. Analyze Network
2. Network Traffic Analysis
3. OS Hardening Techniques
4. Analyze Network Attack
5. Network Hardening
6. Risk Assessment Report
7. NIST Cybersecurity Framework
Assignments:
Analyze Network Layer Communication
As a cybersecurity analyst supporting a client-facing IT services organization, I investigated reports from multiple end users who were unable to access the website www.yummyrecipesforme.com, consistently receiving a “destination port unreachable” error. After reproducing the issue myself, I initiated a packet‑level analysis using tcpdump to determine which network protocol was failing. When the webpage was requested, the browser first issued a DNS lookup using UDP to query the DNS server for the domain’s IP address. This is standard behavior for DNS resolution. Once the IP address is obtained, the browser would normally initiate an HTTPS (TCP/443) session with the web server.
However, the packet capture revealed that each outbound UDP request to port 53 on the DNS server triggered an immediate ICMP error response stating “udp port 53 unreachable.” This indicates that the DNS server was not accepting or processing DNS queries—either because the service was offline, misconfigured, or blocked by a network control device. As a result, DNS resolution failed, preventing the browser from obtaining the destination IP and ultimately causing the website to be inaccessible.
TCPDUMP PACKET CAPTURE LOG
Breakdown information of packet capture log
The first two lines of the log file show the initial outgoing request from your computer to the DNS server requesting the IP address of yummyrecipesforme.com. This request is sent in a UDP packet.
The third and fourth lines of the log show the response to your UDP packet. In this case, the ICMP 203.0.113.2 line is the start of the error message indicating that the UDP packet was undeliverable to port 53 of the DNS server.
In front of each request and response, you find timestamps that indicate when the incident happened. In the log, this is the first sequence of numbers displayed: 13:24:32.192571. This means the time is 1:24 p.m., 32.192571 seconds.
After the timestamps, you will find the source and destination IP addresses. In the first line, where the UDP packet travels from your browser to the DNS server, this information is displayed as: 192.51.100.15 > 203.0.113.2.domain
The IP address to the left of the greater‑than symbol is the source address (your computer). The IP address to the right is the destination (the DNS server). For the ICMP error response, the source address is 203.0.113.2 and the destination is 192.51.100.15.
After the source and destination IP addresses, there can be additional details such as the protocol, source port number, and flags. In the first line of the error log, the query identification number appears as 35084. The plus sign after the query ID indicates flags associated with the UDP message. The “A?” indicates a DNS request for an A record, which maps a domain name to an IP address. The third line displays the protocol of the response message: ICMP, followed by an ICMP error message.
The error message “udp port 53 unreachable” appears in the last line. Port 53 is used for DNS service. The word “unreachable” indicates that the UDP message requesting the IP address for www.yummyrecipesforme.com did not reach the DNS server because no service was listening on port 53.
The remaining lines in the log indicate that ICMP packets were sent two more times, but the same delivery error occurred each time.
Cybersecurity Incident Report: Network Traffic Analysis
Part 1: Summary of the Problem Found in the tcpdump Log
Analysis of the tcpdump capture shows that the client system initiates a DNS lookup for yummyrecipesforme.com using UDP as expected for standard DNS queries. Each outbound DNS request appears in the first two lines of the log and is followed immediately by an ICMP Type 3, Code 3 response—“udp port 53 unreachable.” This ICMP error indicates that the DNS server at the destination IP is not accepting traffic on UDP/53, the port required for DNS resolution.
Additional packet details reinforce the DNS failure. The query identification number 35084 includes a “+” flag, indicating DNS query options, and the “A?” flag confirms that the client is attempting to resolve an IPv4 A‑record. Because every DNS request results in an ICMP unreachable response, the DNS resolution process cannot complete, preventing the client from obtaining the web server’s IP address. This behavior strongly suggests that the DNS service is offline, misconfigured, or being actively blocked.
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Part 2: Analysis of the Data and Cause of the Incident
The incident occurred at 13:24, when customers reported receiving a “destination port unreachable” error while attempting to access the website. Packet inspection using tcpdump confirmed that all DNS queries to UDP/53 failed, resulting in ICMP unreachable messages. Without successful DNS resolution, the client cannot establish an HTTP or HTTPS session with the target web server.
The root cause is likely one of the following technical failures:
DNS service outage on the authoritative DNS server
Firewall or ACL blocking UDP/53 between the client and DNS server
DoS attack saturating or disabling the DNS service
Misconfiguration preventing the DNS daemon from binding to port 53
Further investigation is required to determine whether the DNS server is down, unreachable due to network filtering, or intentionally targeted by an attack.
OS Hardening Techniques
As a cybersecurity analyst supporting yummyrecipesforme.com, I investigated a security incident in which a former employee compromised the organization’s web infrastructure and deployed malware through the site’s source code. The attacker gained unauthorized access to the hosting environment by performing a brute‑force attack against the administrative login interface, repeatedly submitting default and commonly used credentials until authentication succeeded. Once authenticated, the attacker accessed the web administration panel, modified the site’s HTML and JavaScript, and injected a malicious script designed to automatically trigger a download prompt for an executable payload whenever a user visited the site. After embedding the malicious code, the attacker changed the administrator password to maintain persistence and prevent legitimate access.
Within hours, customers reported that the website prompted them to download a file claiming to provide free recipes. After executing the file, users observed browser redirection and system performance degradation—indicators of malware execution and possible resource hijacking. Concurrently, the website owner was unable to authenticate to the admin panel, confirming unauthorized credential modification.
To analyze the compromise safely, I deployed a sandbox environment and captured network activity using tcpdump. Upon navigating to the legitimate domain, the injected script immediately initiated a forced download of a spoofed “browser update” executable. After execution, the browser issued new outbound HTTP requests and was redirected to greatrecipesforme.com, a malicious domain hosting the attacker’s payload. The captured packet data confirmed the redirection sequence and validated that the malicious executable altered the client’s browsing behavior, completing the attacker’s infection chain.
DOCUMENT THE INCIDENT
Several customers reported to the helpdesk that when accessing the website, they were presented with an unsolicited download prompt for an executable file advertised as providing access to new recipes. After executing the file, users experienced significant system performance degradation, indicating potential malware execution on their endpoints. Concurrently, the website owner attempted to authenticate to the administrative interface but found that their credentials no longer worked, suggesting unauthorized modification of account access.
To investigate the incident safely, a cybersecurity analyst initiated a controlled sandbox environment and captured network activity using tcpdump while interacting with the compromised site. Upon loading the webpage, the analyst immediately received a forced download prompt for an executable masquerading as a legitimate recipe file. After executing the file within the sandbox, the browser generated outbound HTTP requests and was automatically redirected to a secondary domain, greatrecipesforme.com, which hosted the malicious payload.
Packet analysis confirmed that the browser initially performed a DNS lookup for yummyrecipesforme.com and established a standard HTTP session. Immediately following execution of the downloaded file, the tcpdump logs showed a clear deviation in network behavior: the client initiated new DNS queries and HTTP requests to greatrecipesforme.com, indicating that the malware altered the browser’s traffic flow and redirected the session to the attacker‑controlled infrastructure.
A senior cybersecurity professional performed a code review of both the legitimate and malicious sites, as well as the downloaded executable. The analysis revealed that the attacker had injected malicious JavaScript into the legitimate site to trigger the forced download. Given that the website owner was locked out of the administrative account, the team concluded that the attacker likely used a brute‑force attack to compromise the admin credentials, escalate privileges, and modify the site’s source code. Execution of the malicious file resulted in endpoint compromise and unauthorized redirection to the attacker’s domain.
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Recommended Remediations for Brute‑Force Attacks:
To mitigate brute‑force attacks and prevent similar compromises in the future, the following technical controls are recommended:
Enforce password history restrictions: Prevent reuse of previous or default passwords to eliminate the possibility of attackers exploiting predictable or legacy credentials.
Implement mandatory password rotation: Require periodic password changes to reduce the window of opportunity for attackers who may have obtained or guessed valid credentials.
Deploy multi‑factor authentication (MFA): Require users to authenticate with both a password and a one‑time passcode (OTP) delivered via email or mobile device. MFA significantly reduces the effectiveness of brute‑force attacks by adding an additional authentication factor that cannot be obtained through password guessing alone.
Analyze Network Attacks
As a security analyst supporting a high‑traffic travel agency website, I received an automated alert from our monitoring system indicating abnormal behavior on the production web server. When I attempted to access the site for validation, the browser returned a connection timeout, suggesting that the server was no longer responding to inbound HTTP requests.
To determine the root cause, I initiated a packet capture using a network analysis tool and inspected traffic flows between client systems and the web server. The capture revealed a large volume of unsolicited TCP SYN packets originating from an unknown external IP address. These SYN packets were being transmitted at a rate far exceeding normal traffic patterns, overwhelming the server’s ability to complete the TCP three‑way handshake. As a result, the server’s connection queue became saturated, preventing legitimate clients from establishing sessions—behavior consistent with a SYN flood Denial‑of‑Service (DoS) attack.
To stabilize the environment, I temporarily removed the server from the network to allow its resources to recover. I then implemented an immediate containment measure by blocking the malicious source IP at the firewall. While this mitigated the active traffic, I recognized that IP‑based blocking is only a short‑term control, as attackers can easily rotate or spoof source addresses.
After restoring service, I escalated the incident to my manager and initiated a deeper analysis. Our team reviewed the packet capture in Wireshark to identify traffic patterns, confirm the attack type, and differentiate between a single‑source DoS attack and a distributed (DDoS) variant. The consistent SYN flood pattern from a single origin strongly indicated a targeted DoS attack against the web server.
This incident demonstrates my ability to analyze malicious network activity, respond to service‑impacting attacks, and implement both immediate and strategic defensive measures to protect organizational infrastructure.
Analysis of Network Hardening
As a security analyst supporting a large social media organization, I conducted a post‑incident assessment following a significant data breach that exposed customer information, including names and physical addresses. The breach highlighted critical weaknesses in the organization’s security posture and underscored the need for immediate implementation of comprehensive network‑hardening controls.
During my technical review of the environment, I identified four major vulnerabilities contributing to the organization’s elevated risk profile:
Password reuse and credential sharing among employees, increasing the likelihood of unauthorized access and credential compromise.
A database administrator account still configured with its default password, creating a high‑severity attack vector for privilege escalation.
Firewalls operating without defined inbound and outbound filtering rules, leaving the network perimeter exposed to unauthorized traffic flows.
Absence of multifactor authentication (MFA) across critical systems, reducing the effectiveness of identity verification and enabling credential‑based attacks.
If left unmitigated, these deficiencies significantly increase the probability of recurring data breaches, unauthorized access, and further compromise of sensitive customer data.
As part of this assessment, I evaluated available network‑hardening tools and selected the most effective controls for this environment. I also recommended targeted security practices—including credential management improvements, firewall rule implementation, and MFA deployment—to reduce attack surface and strengthen overall resilience.
This task demonstrates my ability to identify systemic vulnerabilities, perform structured risk assessments, and propose technically sound remediation strategies to enhance an organization’s security posture. It reflects my commitment to enforcing cybersecurity best practices and protecting sensitive data against evolving threats.
Network Hardening Tools
Using the NIST cybersecurity framework(CSF) to respond to a security incident
In my role as a cybersecurity analyst for a multimedia services organization specializing in web design, graphic design, and social media marketing, I responded to a significant Distributed Denial of Service (DDoS) incident that disrupted internal network operations for approximately two hours. The attack resulted in a complete loss of network availability, preventing employees from accessing critical internal resources.
During the event, network monitoring tools indicated a sudden and sustained surge of ICMP echo‑request packets, far exceeding normal traffic baselines. This abnormal spike in ICMP traffic saturated network bandwidth and exhausted server processing capacity, effectively preventing legitimate internal traffic from reaching any network services. The pattern and volume of traffic were consistent with an ICMP‑based DDoS attack.
The incident response team initiated immediate containment actions, including blocking inbound ICMP traffic at the perimeter, disabling non‑essential network services to reduce load, and restoring critical services once resource utilization stabilized. These measures successfully mitigated the active attack and restored partial network functionality.
A post‑incident investigation revealed that the attacker exploited an unconfigured firewall, which lacked proper ICMP filtering and rate‑limiting controls. This misconfiguration allowed the adversary to flood the network with ICMP packets from multiple distributed sources, overwhelming the infrastructure and causing the service outage.
To strengthen the organization’s defensive posture and prevent recurrence, the network security team implemented several technical controls:
ICMP rate‑limiting rules were added to the firewall to restrict the volume of inbound ICMP packets and prevent resource exhaustion.
Source IP verification was enabled to detect and block spoofed IP addresses commonly used in DDoS amplification attacks.
Network monitoring software was deployed to provide real‑time visibility into traffic anomalies and early detection of volumetric attacks.
Intrusion Detection and Prevention Systems (IDS/IPS) were configured to identify and filter malicious ICMP traffic based on behavioral signatures and packet characteristics.
This incident highlights the critical need for properly configured perimeter defenses, continuous traffic inspection, and a layered network‑security architecture to ensure service availability and protect organizational infrastructure from distributed attacks. The disruption demonstrated how gaps in network configuration can be exploited to degrade performance, overwhelm resources, and compromise operational continuity.
As a cybersecurity analyst, I am leveraging the lessons learned from this event to develop a comprehensive network‑security enhancement plan aligned with the National Institute of Standards and Technology (NIST) Cybersecurity Framework (CSF). This plan focuses on strengthening our defensive posture across the CSF functional areas—Identify, Protect, Detect, Respond, and Recover—by implementing hardened configurations, improving visibility into network activity, and deploying advanced security controls designed to mitigate similar threats in the future.
NIST Cybersecurity Framework key areas:
Identify: Identifying security risks through routine audits of internal networks, systems, devices, and access privileges to uncover potential security gaps.
Protect: Safeguarding internal assets through the implementation of policies, procedures, training, and tools aimed at mitigating cybersecurity threats.
Detect: Enhancing our capability to identify potential security incidents and bolstering monitoring systems to expedite detection.
Respond: Developing strategies to promptly contain, neutralize, and analyze security incidents, while concurrently making improvements to our overall security procedures.
Recover: Establishing protocols to restore affected systems to their normal operation and to recover any data or assets that may have been impacted during an incident.
By aligning our approach with the NIST Cybersecurity Framework, I will develop a robust, defense‑in‑depth security strategy designed to strengthen our network against emerging and persistent threats. Successfully completing this initiative demonstrates my capability in mitigating DDoS attack vectors and reinforces my commitment to implementing resilient security controls that safeguard critical systems and sensitive digital assets.
NIST Cybersecurity Framework Analysis