CEH Hard Questions — 25 Difficult Questions

Question 1

A security analyst runs the Nmap command: nmap -sI 192.168.1.50 -p 80 10.0.0.1. The scan completes, but the target shows no open ports. What is the MOST likely explanation?

Accepted Answer

The zombie host is not truly idle, causing false results. The -sI flag in Nmap performs an idle scan, which relies on a zombie host (192.168.1.50) with a globally predictable IP ID sequence to probe the target. If the zombie host is not truly idle—meaning it is sending or receiving other traffic during the scan—its IP ID values will increment unpredictably, corrupting the side-channel analysis and causing Nmap to report all ports as filtered or closed. This is the most likely reason for the false 'no open ports' result.

Answer

The analyst used the wrong port number

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The target has a firewall blocking the decoy packets

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The target host is offline

Question 2

A security team suspects a session hijacking attack. The analyst examines network traffic and sees packets with sequence numbers that increment by predictable values. Which attack is MOST likely occurring?

Accepted Answer

TCP sequence prediction. TCP sequence prediction attacks exploit the ability to guess the next sequence number in a TCP connection, allowing an attacker to inject forged packets and hijack the session. The analyst observed packets with sequence numbers incrementing by predictable values, which is the hallmark of weak or static sequence number generation in older TCP implementations.

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ARP poisoning

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DNS spoofing

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MAC flooding

Question 3

Which THREE of the following are valid techniques for covering tracks after compromising a system? (Select 3 correct answers)

Accepted Answer

Clearing event logs using wevtutil. A is correct because wevtutil is a Windows command-line utility used to manage event logs. After compromising a system, an attacker can use 'wevtutil cl' followed by a log name (e.g., 'wevtutil cl System') to clear specific event logs, thereby erasing evidence of their activities. This is a direct and common technique for covering tracks by removing forensic artifacts.

Answer

Exploiting SUID binaries to gain root

Answer

Disabling Windows Defender via Group Policy

Question 4

Which THREE of the following are effective DDoS mitigation techniques? (Select 3)

Accepted Answer

Anycast network distribution. Anycast network distribution is effective because it routes traffic to the nearest or best-performing server among multiple geographically dispersed nodes, using BGP to announce the same IP address from multiple locations. This disperses attack traffic across many servers, preventing any single node from being overwhelmed and absorbing volumetric DDoS attacks at the network edge.

Answer

Disabling TCP SYN cookies

Answer

Using a single server with high bandwidth

Question 5

During a penetration test, you gain initial access to a Linux server as a low-privileged user. The target runs a vulnerable SUID binary owned by root. Which of the following is the MOST effective method to escalate privileges?

Accepted Answer

Exploit the SUID binary to execute commands as root. The SUID binary owned by root runs with root privileges regardless of the user executing it. Exploiting a vulnerable SUID binary (e.g., via command injection, buffer overflow, or misconfigured capabilities) allows the low-privileged user to execute arbitrary commands as root, directly escalating privileges. This is the most effective method because it leverages a known privilege escalation vector specific to Linux SUID binaries.

Answer

Perform an SMTP VRFY attack to enumerate users

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Use enum4linux to enumerate SMB shares

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Run 'sudo -l' to list sudo privileges

Question 6

A forensic analyst finds a system where the user's password hash was obtained and cracked offline. The attacker then used stolen credentials to log in and run `wevtutil cl system`. What is the purpose of this command?

Accepted Answer

Clear the System event log. The `wevtutil cl system` command clears the System event log on Windows. After cracking the user's password hash offline, the attacker logs in with stolen credentials and runs this command to erase forensic evidence of their activities, such as logon events or service failures, from the System log. This is a common post-exploitation step to hinder incident response.

Answer

Remove scheduled tasks

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Delete the SAM database

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Disable Windows Defender

Question 7

An attacker uses an idle scan with Nmap to probe a target. This technique relies on a third-party host with a predictable IP ID sequence to infer port states. Which Nmap flag enables an idle scan?

Accepted Answer

-sI. The idle scan (-sI) leverages a third-party host (zombie) with a predictable IP ID sequence to indirectly probe a target's ports. By spoofing the zombie's IP and observing changes in its IP ID counter, Nmap can infer whether a port is open, closed, or filtered without sending packets directly from the attacker's IP.

Answer

-sS

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-sA

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-sT

Question 8

An ethical hacker is analyzing a suspicious file using static analysis. Which of the following actions is part of static malware analysis?

Accepted Answer

Examining the file's strings and metadata without executing it. Static malware analysis involves examining the file without executing it. Option C is correct because analyzing strings and metadata (e.g., file headers, embedded URLs, IP addresses, or suspicious function calls) is a core static analysis technique, often performed using tools like `strings`, `binwalk`, or `PEview`. This approach avoids the risks of execution and helps identify indicators of compromise (IOCs) before dynamic analysis.

Answer

Running the file in a sandboxed environment and monitoring its behavior

Answer

Uploading the file to VirusTotal for scanning

Answer

Using Wireshark to capture packets sent by the file

Question 9

A security analyst observes that an Nmap SYN scan against a target network returns all ports as 'filtered'. The analyst suspects an IDS/IPS is dropping inbound SYN packets. Which Nmap technique would MOST likely bypass this detection while still identifying open ports?

Accepted Answer

Enable IP fragmentation with the -f flag. When an IDS/IPS drops inbound SYN packets, a standard SYN scan (-sS) is detected because the probe packets are easily recognized. Enabling IP fragmentation with the -f flag splits the TCP header across multiple fragments, making it harder for the IDS/IPS to reassemble and inspect the full packet, thus potentially bypassing the filter while still allowing Nmap to determine open ports based on responses.

Answer

Use the -sU flag for UDP scanning

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Use the -sT flag for a TCP connect scan

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Increase scanning speed with -T5

Question 10

During a penetration test, you discover an LDAP server on port 389 that allows anonymous binds. Which of the following enumeration techniques would provide the MOST comprehensive information about the directory structure?

Accepted Answer

Use ldapsearch to query the directory for all attributes. `ldapsearch` with anonymous bind allows querying the LDAP directory for all attributes and entries, providing comprehensive information about the directory structure, including user accounts, groups, organizational units, and other objects. LDAP servers on port 389 often expose the entire directory tree when anonymous binds are permitted, making `ldapsearch` the most effective enumeration technique.

Answer

Run nmap with the smb-enum-shares script

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Perform a DNS zone transfer

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Use net view to list domain resources

Question 11

A security engineer needs to configure a web server to support Perfect Forward Secrecy (PFS) for HTTPS connections. Which of the following key exchange methods should be prioritized?

Accepted Answer

Elliptic Curve Diffie-Hellman Ephemeral (ECDHE). ECDHE is prioritized for Perfect Forward Secrecy because it generates a unique, ephemeral session key for each TLS handshake using elliptic curve cryptography, ensuring that if the server's long-term private key is compromised, past session keys remain secure. Unlike static Diffie-Hellman, ECDHE does not reuse key material, and it offers stronger security per bit compared to traditional DH, making it the recommended choice for PFS in modern HTTPS configurations.

Answer

Diffie-Hellman (DH) key exchange

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Pre-Shared Key (PSK)

Answer

RSA key exchange

Question 12

Refer to the exhibit. A security analyst notices multiple ESTABLISHED connections on port 443 from different external IPs to the same process ID. What type of attack is most likely occurring?

Accepted Answer

Distributed denial-of-service (DDoS) attack. Multiple ESTABLISHED connections on port 443 (HTTPS) from different external IPs to the same process ID indicate a distributed denial-of-service (DDoS) attack. In a DDoS, many compromised hosts (botnet) simultaneously establish legitimate TCP handshakes and maintain connections to exhaust server resources, such as connection slots or memory, at the application layer. The key clue is the diversity of source IPs targeting a single process, which is characteristic of a coordinated flood from many distinct sources.

Answer

SSL/TLS renegotiation DoS

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Slowloris attack

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Man-in-the-middle attack

Question 13

During a penetration test, a tester uses Nmap with the command: nmap -sS -D RND:10 192.168.1.100. After the scan, the IDS logs show multiple SYN packets from different source IPs hitting the target. However, the tester's true IP is not among them. Which of the following techniques is being used?

Accepted Answer

Decoy scan. The command `nmap -sS -D RND:10` performs a SYN stealth scan with 10 randomly generated decoy IP addresses. The IDS logs show multiple SYN packets from different source IPs, but the tester's true IP is not among them because Nmap sends the decoy packets with spoofed source addresses while the real scan packet is interleaved among them. This is the definition of a decoy scan, which aims to obscure the attacker's true origin by blending it with fake sources.

Answer

Idle scan

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SYN flood

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Fragmentation attack

Question 14

During a ransomware incident response, a forensic analyst recovers a suspicious file that appears to be a PE executable. The analyst wants to quickly check if the file is known malware without executing it. Which of the following is the BEST first step?

Accepted Answer

Submit the file hash to VirusTotal. Submitting the file hash to VirusTotal is the best first step because it leverages aggregated antivirus engines and threat intelligence to quickly determine if the file is known malware, without any execution risk. This approach is fast, non-invasive, and provides immediate reputation data from over 70 security vendors, making it ideal for triage during incident response.

Answer

Disassemble the file using IDA Pro

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Perform static analysis using PEiD to identify compiler and packer

Answer

Run the file in a sandbox and observe its behavior

Question 15

An analyst runs the following command: `tcpdump -i eth0 src host 192.168.1.10 and dst port 80 -w http_traffic.pcap`. What is the primary purpose of this command?

Accepted Answer

To capture only HTTP traffic from a specific source IP and save it to a file. The command `tcpdump -i eth0 src host 192.168.1.10 and dst port 80 -w http_traffic.pcap` uses a BPF (Berkeley Packet Filter) expression to capture only packets originating from source IP 192.168.1.10 and destined for TCP port 80 (HTTP). The `-w` flag writes the filtered packets directly to a pcap file, not to standard output, making the primary purpose to capture and save specific HTTP traffic for later analysis.

Answer

To perform a man-in-the-middle attack on HTTP traffic

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To capture all traffic on eth0 and display it in real-time

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To analyze the payload of HTTP packets in real-time

Question 16

You are performing a penetration test and need to quickly scan a large IP range (e.g., 10.0.0.0/8) for open ports 80 and 443. Which tool is BEST suited for this high-speed scanning task?

Accepted Answer

Masscan. Masscan is the best tool for this task because it is designed specifically for high-speed port scanning, capable of transmitting packets at rates exceeding 10 million packets per second, which is necessary to scan a /8 subnet (over 16 million IPs) for ports 80 and 443 in a reasonable timeframe. Unlike Nmap, which optimizes for accuracy and service detection, Masscan uses asynchronous raw socket transmission and can be tuned with the --rate parameter to maximize throughput, making it ideal for large-scale reconnaissance.

Answer

OpenVAS

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hping3

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Nmap

Question 17

During a penetration test, you enumerate a Linux NFS server and discover that the /export directory is mounted with 'no_root_squash' and 'world_readable' permissions. Which of the following actions would allow you to escalate to root access on the NFS client?

Accepted Answer

Mount the share, create a setuid binary owned by root, then execute it on the client. Mounting an NFS export with 'no_root_squash' means that root on the client is treated as root on the server. By creating a setuid binary owned by root on the mounted share, any user on the client can execute that binary and gain root privileges on the client system, effectively escalating from a regular user to root.

Answer

Create a symbolic link to /etc/shadow on the server from the client

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Use 'showmount -e' to list exports and then mount the share with 'mount -t nfs -o vers=3'

Answer

Run 'sudo nmap --script nfs-ls' to list files on the export

Question 18

A security analyst is investigating a compromised Linux system. The /var/log/auth.log file appears to be truncated, and the timestamps on several binaries in /bin/ have been modified. Which of the following tools or techniques is the attacker MOST likely using to cover tracks?

Accepted Answer

Rootkit. The attacker is most likely using a rootkit to cover tracks because rootkits are designed to hide malicious activity by intercepting system calls (e.g., via LD_PRELOAD or kernel modules) to hide processes, files, and network connections. The truncated auth.log and modified timestamps on binaries in /bin/ indicate the rootkit is actively tampering with system logs and file metadata to evade detection, which aligns with rootkit behavior rather than simpler tools.

Answer

Timestamp manipulation tool

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Steganography

Answer

Log cleaner script

Question 19

An organization's security team observes a surge in outgoing DNS queries to external servers from a single internal host, with each query returning unusually large responses (e.g., 4000 bytes). The host is not configured as a DNS resolver. Which attack is MOST likely occurring?

Accepted Answer

DNS tunneling. The scenario describes a single internal host initiating a surge of outgoing DNS queries to external servers and receiving unusually large responses (e.g., 4000 bytes). This behavior, particularly from a host not configured as a DNS resolver, is a strong indicator of DNS tunneling. In DNS tunneling, a compromised host establishes a covert communication channel by encapsulating data within DNS queries and responses, often for data exfiltration or command and control. Large DNS responses, frequently utilizing record types like TXT, are commonly employed to transfer significant amounts of data back to the compromised host. DNS amplification DDoS attacks, in contrast, involve an attacker spoofing a victim's IP address to send small queries to open resolvers, causing the victim to be overwhelmed by large, unsolicited responses; the victim does not actively send the initial queries in this scenario.

Answer

DNS cache poisoning

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DNS zone transfer

Answer

DNS amplification DDoS attack

Question 20

Which THREE of the following are common countermeasures to prevent DNS zone transfers from being abused? (Choose THREE.)

Accepted Answer

Restrict zone transfers to only specific authorized secondary name servers. Restricting zone transfers to only specific authorized secondary name servers (Option B) is a fundamental access control measure that prevents unauthorized hosts from requesting a full copy of the DNS zone data, thereby mitigating information leakage during reconnaissance. Implementing split DNS (Option C) limits the information an external attacker can gain from a successful zone transfer by presenting different views of DNS data to internal and and external clients. Using Transaction Signatures (TSIG) (Option D) provides cryptographic authentication for zone transfer requests, ensuring that only trusted secondary servers with the shared secret key can perform transfers.

Answer

Enable DNS recursion on the name server

Answer

Configure the name server to allow zone transfers from any host