Quick Answer
The answer is TCP session hijacking. This is the correct choice because the attack relies on predicting the sequence numbers used to track the state of a TCP connection, allowing the attacker to inject forged packets that the receiving host accepts as legitimate traffic from the trusted party. By successfully guessing the next expected sequence number, the attacker can effectively impersonate the authenticated host and take over the active session without needing credentials. On the Certified Ethical Hacker CEH exam, this scenario tests your understanding of how TCP vulnerabilities are exploited at the transport layer, often appearing in questions that contrast hijacking with simpler denial-of-service or spoofing attacks. A common trap is confusing this with a blind spoofing attack, but the key distinction is that session hijacking involves actively injecting data into an ongoing connection, not just sending packets from a spoofed address. Memory tip: think “sequence prediction equals session injection” — if the attacker is predicting numbers to insert packets, it is hijacking, not just spoofing.
This CEH practice question tests your understanding of malware, social engineering and network attacks. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A penetration tester successfully predicts the TCP sequence numbers of a target and sends crafted packets to impersonate a trusted host. Which type of attack is this?
ARP poisoning
Why wrong: ARP poisoning manipulates ARP tables, not TCP sequence prediction.
TCP sequence prediction attack
Why wrong: This is a step in session hijacking, but the attack described is the broader session hijack.
TCP session hijacking
Session hijacking uses sequence prediction to take over a TCP session.
DNS spoofing
Why wrong: DNS spoofing corrupts DNS responses, not TCP sequence prediction.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
TCP session hijacking
TCP session hijacking involves predicting sequence numbers to inject packets and take over a session. It allows the attacker to impersonate one of the communicating parties.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
ARP poisoning
TCP sequence prediction attack
Why it's wrong here
This is a step in session hijacking, but the attack described is the broader session hijack.
TCP session hijacking
DNS spoofing
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CEH NAT questions on configuration and troubleshooting.
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FAQ
Malware, Social Engineering and Network Attacks — This question tests Malware, Social Engineering and Network Attacks — Static NAT maps one inside address to one outside address..
The correct answer is: TCP session hijacking — TCP session hijacking involves predicting sequence numbers to inject packets and take over a session. It allows the attacker to impersonate one of the communicating parties.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CEH NAT questions on configuration and troubleshooting.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 21, 2026
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