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A systems administrator receives reports of an internet-accessible Linux server that is running very sluggishly. The administrator examines the server, sees a high amount of memory utilization, and suspects a DoS attack related to half-open TCP sessions consuming memory. Which of the following tools would best help to prove whether this server was experiencing this behavior?
TCPDump is the best tool to prove whether the server was experiencing a DoS attack related to half-open TCP sessions consuming memory. TCPDump is a command-line tool that can capture and analyze network traffic, such as TCP, UDP, and ICMP packets. TCPDump can help the administrator to identify the source and destination of the traffic, the TCP flags and sequence numbers, the packet size and frequency, and other information that can indicate a DoS attack. A DoS attack related to half-open TCP sessions is also known as a SYN flood attack, which is a type of volumetric attack that aims to exhaust the network bandwidth or resources of the target server by sending a large amount of TCP SYN requests and ignoring the TCP SYN-ACK responses. This creates a backlog of half-open connections on the server, which consume memory and CPU resources, and prevent legitimate connections from being established12. TCPDump can help the administrator to detect a SYN flood attack by looking for a high number of TCP SYN packets with different source IP addresses, a low number of TCP SYN-ACK packets, and a very low number of TCP ACK packets34. Reference: SYN flood DDoS attack | Cloudflare, What is a SYN flood attack and how to prevent it? | NETSCOUT, TCPDump - A Powerful Tool for Network Analysis and Security, How to Detect a SYN Flood Attack with TCPDump
A security analyst runs the following command:
# nmap -T4 -F 192.168.30.30
Starting nmap 7.6
Host is up (0.13s latency)
PORT STATE SERVICE
23/tcp open telnet
443/tcp open https
636/tcp open ldaps
Which of the following should the analyst recommend first to harden the system?
Comprehensive Detailed The nmap scan results show that Telnet (port 23) is open. Telnet transmits data, including credentials, in plaintext, which is insecure and should be disabled to enhance security. Here's an explanation of each option:
A . Disable all protocols that do not use encryption
Disabling unencrypted protocols (such as Telnet) reduces exposure to man-in-the-middle (MITM) attacks and credential sniffing. Telnet should be replaced with a secure protocol like SSH, which provides encryption for transmitted data.
B . Configure client certificates for domain services
While client certificates enhance authentication security, they are more relevant to services like LDAP over SSL (port 636), which is already secure. This would not address the Telnet vulnerability.
C . Ensure that this system is behind a NGFW
A Next-Generation Firewall (NGFW) provides enhanced network security, but it may not mitigate the risks of unencrypted protocols if they are allowed internally.
D . Deploy a publicly trusted root CA for secure websites
Public root CAs are used for website authentication and encryption, relevant only if this system is hosting a publicly accessible HTTPS service. It would not impact Telnet security.
CIS Controls: Recommendations on secure configurations, especially the use of encrypted protocols.
NIST SP 800-47: Security considerations for network protocols, emphasizing encrypted alternatives like SSH over Telnet.
A security analyst is trying to identify possible network addresses from different source networks belonging to the same company and region. Which of the following shell script functions could help achieve the goal?
The shell script function that could help identify possible network addresses from different source networks belonging to the same company and region is:
function y() { dig $(dig -x $1 | grep PTR | tail -n 1 | awk -F ''.in-addr'' '{print $1}').origin.asn.cymru.com TXT +short }
This function takes an IP address as an argument and performs two DNS lookups using the dig command. The first lookup uses the -x option to perform a reverse DNS lookup and get the hostname associated with the IP address. The second lookup uses the origin.asn.cymru.com domain to get the autonomous system number (ASN) and other information related to the IP address, such as the country code, registry, or allocation date. The function then prints the IP address and the ASN information, which can help identify any network addresses that belong to the same ASN or region
During a scan of a web server in the perimeter network, a vulnerability was identified that could be exploited over port 3389. The web server is protected by a WAF. Which of the following best represents the change to overall risk associated with this vulnerability?
Port 3389 is commonly used by Remote Desktop Protocol (RDP), which is a service that allows remote access to a system. A vulnerability on this port could allow an attacker to compromise the web server or use it as a pivot point to access other systems. However, if the firewall blocks this port, the risk of exploitation is reduced.
A threat hunter seeks to identify new persistence mechanisms installed in an organization's environment. In collecting scheduled tasks from all enterprise workstations, the following host details are aggregated:
Which of the following actions should the hunter perform first based on the details above?
The first step should be to perform a public search for malware reports on taskhw.exe, as this file is suspicious for several reasons: it is located in a non-standard path, it has a high CPU usage, it is signed by an unknown entity, and it is only present on one host. A public search can help to determine if this file is a known malware or a legitimate program. If it is malware, the hunter can then take appropriate actions to remove it and prevent further damage. The other options are either premature or ineffective, as they do not provide enough information to assess the threat level of taskhw.exe.Reference:Cybersecurity Analyst+ - CompTIA,taskhw.exe Windows process - What is it? - file.net,Taskhostw.exe - What Is Taskhostw.exe & Is It Malware? - MalwareTips Forums
462 questions covering all exam domains, starting from $20
Exam domains verified against: Official CompTIA CS0-003 exam guide, last checked September 2026.
Analyze network and system architecture as it applies to threat detection and response. Use tools and techniques to identify malicious activity and distinguish between genuine attacks and false positives in security operations.
Execute vulnerability scanning and assessment to discover weaknesses in systems and applications. Prioritize vulnerabilities based on risk and recommend specific technical controls to remediate them.
Sample question from this domain above: Q5
Perform tactical incident response activities and follow the incident management lifecycle from preparation through post-incident review. Apply frameworks like MITRE ATT&CK to understand attack methodology.
Report findings from vulnerability assessments and incident investigations to stakeholders in actionable terms. Communicate security risks and remediation status in ways that inform business decisions.
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