CEH Practice Exam 4 — 20 Questions

Question 1

A security analyst runs the command 'tcpdump -i eth0 -n host 10.0.0.5 and port 80' and sees many packets with the SYN flag set but no corresponding ACK. Which attack is likely occurring?

Accepted Answer

SYN flood. The command captures TCP packets on port 80 with the SYN flag set but no corresponding ACK, which indicates that the target is receiving SYN requests but never completing the three-way handshake. This is the hallmark of a SYN flood attack, where the attacker sends a high volume of SYN packets to exhaust the server's connection queue, preventing legitimate connections.

Answer

ICMP flood

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UDP flood

Answer

Ping of Death

Question 2

A security analyst notices a significant increase in outbound traffic from an internal server to multiple external IPs on port 443. The server is not a web server and should not be initiating such connections. Which type of malware is MOST likely causing this behavior?

Accepted Answer

A backdoor Trojan. A backdoor Trojan is designed to give an attacker remote control over an infected system, often using outbound connections on common ports like 443 (HTTPS) to blend in with normal traffic. Since the server is not a web server and should not be initiating outbound HTTPS connections, this anomalous behavior strongly indicates a backdoor Trojan is exfiltrating data or receiving commands via encrypted channels.

Answer

A boot sector virus

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A fileless virus

Answer

A worm

Question 3

A security analyst runs `nbtstat -A 192.168.1.10` and receives output showing a table with names like COMPUTER<00>, COMPUTER<20>, and DOMAIN<1B>. What type of information has the analyst gathered?

Accepted Answer

NetBIOS names and their associated service types. The `nbtstat -A` command performs a NetBIOS name table lookup against the target IP address using the NetBIOS over TCP/IP (NBT) protocol. The output displays NetBIOS names (e.g., COMPUTER<00>, COMPUTER<20>, DOMAIN<1B>) along with their associated service type suffixes (hex bytes), which identify the services running on the host, such as Workstation Service (<00>), Server Service (<20>), and Domain Master Browser (<1B>). This allows the analyst to enumerate the host's NetBIOS names and their corresponding service types.

Answer

SMB share lists and open sessions

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DNS records for the host and domain

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ARP cache entries for the subnet

Question 4

A penetration tester uses the following Google dork: intitle:"index of" "backup" site:example.com. What is the MOST likely goal of this search?

Accepted Answer

Locate open directories that might contain sensitive files. The Google dork `intitle:"index of" "backup" site:example.com` targets web servers that have directory listing enabled (indicated by the page title containing 'index of') and that contain a folder or file named 'backup'. This is a classic reconnaissance technique to find open directories where backup files (e.g., database dumps, configuration files) may be inadvertently exposed, potentially containing sensitive data such as credentials or proprietary information.

Answer

Discover email addresses associated with the domain

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Find login pages of the target domain

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Identify subdomains of example.com

Question 5

A security analyst is asked to perform a fast scan of a large network (e.g., /16 subnet) to identify live hosts. Which tool is MOST suitable for this task due to its high speed?

Accepted Answer

Masscan. Masscan is the most suitable tool for this task because it is designed specifically for high-speed scanning of large address spaces, such as a /16 subnet (65,536 hosts). It uses asynchronous transmission and can send packets at rates exceeding 10 million packets per second, making it significantly faster than Nmap for raw host discovery across massive ranges.

Answer

hping3

Answer

Nmap

Answer

Wireshark

Question 6

During a security assessment, you find a Linux binary with the SUID bit set and owned by root. You execute it and obtain a root shell. This is an example of which privilege escalation technique?

Accepted Answer

SUID abuse. The SUID (Set User ID) bit on a binary owned by root allows it to execute with root privileges regardless of the user running it. When you execute such a binary and it spawns a shell, that shell inherits the elevated privileges, effectively granting you a root shell. This is a classic example of SUID abuse, a common privilege escalation technique on Linux systems.

Answer

DLL hijacking

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Kernel exploit

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Token impersonation

Question 7

You are the security lead for a multinational corporation that uses a hybrid cloud architecture with AWS and on-premises data centers. The company recently deployed a fleet of IoT sensors in a remote factory to monitor equipment. These sensors communicate via MQTT to an AWS IoT Core endpoint, which forwards data to an S3 bucket and a DynamoDB table. The factory network is isolated but has a site-to-site VPN to the corporate HQ. Over the past week, the S3 bucket has experienced an unusual number of PUT requests from an IP address that resolves to a known malicious host. The DynamoDB table shows write spikes at odd hours. The MQTT broker logs indicate that some sensors are publishing data with invalid client IDs. Meanwhile, the VPN logs show no anomalies. You need to identify the likely attack vector and recommend a course of action. Which of the following is the BEST course of action?

Accepted Answer

Implement client certificate authentication on AWS IoT Core and revoke any unregistered client IDs.. The attack exploits weak authentication on MQTT connections to AWS IoT Core. By implementing client certificate authentication, you ensure only registered devices with valid X.509 certificates can publish data, directly blocking the malicious PUT requests and write spikes. Revoking unregistered client IDs eliminates the invalid client IDs observed in the MQTT broker logs, closing the primary attack vector without disrupting legitimate sensor traffic.

Answer

Disable the site-to-site VPN and require all traffic to go through a bastion host.

Answer

Move the S3 bucket and DynamoDB table to the on-premises data center to reduce cloud exposure.

Answer

Replace all IoT sensors with new ones that have firmware-level encryption.

Question 8

A penetration tester uses a tool to perform a man-in-the-middle attack by sending forged DNS responses that redirect users to a malicious website. Which tool is MOST likely being used to perform DNS spoofing?

Accepted Answer

Ettercap. Ettercap is a comprehensive suite for man-in-the-middle attacks, including ARP poisoning and DNS spoofing. It can intercept DNS requests and forge fake responses to redirect victims to a malicious IP, making it the correct tool for DNS spoofing.

Answer

Nmap

Answer

Wireshark

Answer

tcpdump

Question 9

Which Nmap flag is used to perform a TCP SYN scan without completing the three-way handshake?

Accepted Answer

-sS. The -sS flag instructs Nmap to perform a TCP SYN scan, which sends a SYN packet to the target port and, upon receiving a SYN/ACK response, sends an RST packet instead of completing the three-way handshake with an ACK. This allows the scanner to determine port states without establishing a full TCP connection, making it faster and less detectable than a full connect scan.

Answer

-sT

Answer

-sU

Answer

-sA

Question 10

During a penetration test, you run `smtp-user-enum -M VRFY -U users.txt -t 10.0.0.10` and receive responses '252 2.5.2 User <username>' for some users and '550 5.1.1 User unknown' for others. What does this indicate?

Accepted Answer

The SMTP server is revealing valid usernames via the VRFY command. The VRFY command in SMTP (RFC 821) asks the server to verify whether a mailbox exists. A response starting with '252' indicates the user is valid, while '550 5.1.1' means the user does not exist. By comparing these responses, the attacker can enumerate valid usernames on the mail server, which is exactly what the output shows.

Answer

The SMTP server is using EXPN instead of VRFY

Answer

The SMTP server is vulnerable to command injection

Answer

The SMTP server is properly configured to prevent enumeration

Question 11

A penetration tester wants to perform a ping sweep on a /24 subnet to identify live hosts. Which command would accomplish this efficiently?

Accepted Answer

nmap -sn 192.168.1.0/24. `nmap -sn` performs a ping sweep (host discovery) without port scanning, sending ICMP echo requests, TCP SYN to port 443, TCP ACK to port 80, and ICMP timestamp requests by default. This efficiently identifies live hosts on a /24 subnet without the overhead of port scanning or OS detection.

Answer

nmap -O 192.168.1.0/24

Answer

nmap -p- 192.168.1.0/24

Answer

nmap -sV 192.168.1.0/24

Question 12

A company wants to protect its network from MAC flooding attacks. Which of the following countermeasures is MOST effective?

Accepted Answer

Enable port security on switches. Enabling port security on switches directly limits the number of MAC addresses that can be learned on a switch port, preventing an attacker from flooding the CAM table with fake MAC addresses. When the configured limit is exceeded, the switch can either drop traffic, shut down the port, or send an alert, effectively stopping the MAC flooding attack at the access layer.

Answer

Use Wireshark to monitor for floods

Answer

Disable CAM table learning

Answer

Implement ARP spoofing detection

Question 13

Which of the following is a well-known attack against the MD5 hash function that allows two different inputs to produce the same hash value?

Accepted Answer

Birthday attack. The birthday attack exploits the birthday paradox in probability theory to find two different inputs that produce the same MD5 hash value (a collision) with significantly less effort than a brute-force preimage attack. For an n-bit hash, the birthday attack requires only about 2^(n/2) operations, making MD5's 128-bit output vulnerable to collisions in roughly 2^64 attempts, which is computationally feasible today.

Answer

Replay attack

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Downgrade attack

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Dictionary attack

Question 14

A security analyst wants to perform passive reconnaissance on a target organization without generating any traffic to the target's network. Which of the following techniques would be MOST appropriate?

Accepted Answer

Performing a WHOIS lookup. WHOIS lookup is a passive reconnaissance technique that queries public databases (e.g., whois.arin.net) for domain registration details without sending any packets to the target's network. It relies on external, publicly available data, thus generating zero traffic to the target organization's infrastructure.

Answer

Running Nmap SYN scan

Answer

Executing hping3 to probe ports

Answer

Using Netcat to connect to a service

Question 15

A network administrator needs to identify all devices on a large corporate network that are running a specific vulnerable version of OpenSSH. The administrator has network access and can use scanning tools. However, scanning the entire network might disrupt operations. Which approach minimizes disruption while accurately identifying the vulnerable hosts?

Accepted Answer

Run a TCP SYN scan on port 22 only, with version detection enabled, across the target IP range.. It targets only TCP port 22 (the default SSH port) with a SYN scan, which is stealthier and faster than a full connect scan, and enables version detection to identify the specific vulnerable OpenSSH version. This minimizes disruption by avoiding scanning unnecessary ports and reduces network load, while accurately pinpointing vulnerable hosts.

Answer

Conduct a full TCP port scan of the entire network using SYN scan.

Answer

Use a ping sweep to identify live hosts, then perform a version scan on each.

Answer

Perform an ARP scan of the entire subnet and then check each host manually.

Question 16

An analyst observes repeated failed login attempts to a Windows server from an internal IP, followed by a successful login using the account 'admin' from the same IP. The analyst checks the Security log and finds Event ID 4624 with Logon Type 3. What type of attack is MOST likely occurring?

Accepted Answer

Dictionary attack on the admin account. Event ID 4624 with Logon Type 3 indicates a network logon (typically SMB or other network resource access). The sequence of repeated failed attempts followed by a successful login from the same internal IP strongly suggests a dictionary (brute-force) attack against the 'admin' account. The attacker systematically tried passwords until one succeeded, which is the hallmark of a dictionary attack.

Answer

SMB relay attack

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Kerberos golden ticket attack

Answer

Pass-the-hash attack

Question 17

Which of the following is the PRIMARY purpose of banner grabbing during the reconnaissance phase?

Accepted Answer

To determine the version of a running service. Banner grabbing is a technique used to extract service banners that often include software name and version details. The primary purpose is to determine the version of a running service, as this information allows an attacker to identify known vulnerabilities specific to that version for further exploitation.

Answer

To discover open ports

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To identify the operating system

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To map the network topology

Question 18

Which type of malware is designed to encrypt files on a victim's system and demand payment for the decryption key?

Accepted Answer

Ransomware. Ransomware is specifically designed to encrypt files on a victim's system using strong cryptographic algorithms (e.g., AES-256 for symmetric encryption, often paired with RSA-2048 for key exchange). After encryption, the malware displays a ransom note demanding payment (typically in cryptocurrency like Bitcoin) in exchange for the decryption key. This matches the description exactly, making option A correct.

Answer

Trojan

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Spyware

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Adware

Question 19

A security analyst captures network traffic and sees a sequence of ARP replies with the same IP address mapping to different MAC addresses within a short period. Which attack is indicated?

Accepted Answer

ARP poisoning. B is correct because ARP poisoning (also called ARP spoofing) involves sending forged ARP replies that map a target IP address (e.g., the default gateway) to the attacker's MAC address. The rapid sequence of ARP replies with the same IP but different MACs is a classic indicator of an active ARP poisoning attack, where the attacker floods the network to corrupt the ARP cache of hosts.

Answer

DNS spoofing

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DHCP starvation

Answer

MAC flooding

Question 20

A penetration tester is performing SNMP enumeration against a network device and wants to retrieve the entire Management Information Base (MIB) tree. Which command should they use?

Accepted Answer

snmpwalk -v 2c -c public 192.168.1.1 .1. `snmpwalk` is specifically designed to retrieve a subtree of MIB objects by performing a series of GETNEXT requests starting from a given OID. Using `.1` as the root OID (which corresponds to the entire ISO tree) with the SNMPv2c community string 'public' will enumerate all accessible OIDs in the MIB tree, effectively dumping the entire Management Information Base.

Answer

snmpset -v 2c -c private 192.168.1.1 1.3.6.1.2.1.1.0 s 'test'

Answer

snmpbulkwalk -v 2c -c public 192.168.1.1 .1

Answer

snmpget -v 2c -c public 192.168.1.1 1.3.6.1.2.1.1