The correct answer is B. Blind Hijacking because the scenario describes injecting crafted TCP packets into an active client-server session to disrupt the legitimate client and take over the connection, without requiring the attacker to see (or fully rely on seeing) the server's responses. In CEH-aligned session hijacking classifications, blind hijacking is an active takeover technique at the TCP/session layer where the attacker forges packets (often with predicted or inferred TCP sequence numbers) to insert data into an existing session and potentially desynchronize the legitimate endpoints. By injecting traffic that causes instability (for example, triggering retransmissions, resets, or sequence/ack mismatch), the attacker can effectively push the victim out of sync or off the session while continuing to communicate with the server as if they were the client.
The key clue is that Sarah "injects crafted TCP packets" into an "active communication," and then the "victim' s connection becomes unstable," after which Sarah's system "maintain[s] communication with the server in place of the legitimate client." This aligns with blind hijacking concepts where the attacker does not simply observe (passive) but actively manipulates the TCP stream to seize control. The attacker's goal is forced takeover of a live session, which often involves sequence prediction and packet injection to become the effective participant while the real client experiences disruption.
Why the other options are incorrect: Passive session hijacking is eavesdropping/monitoring traffic to capture session identifiers without altering the session; it does not involve injecting packets or destabilizing a connection. Man-in-the-Browser is a client-side attack (typically via malware in the browser) that manipulates transactions within the browser context; it is not a TCP packet injection technique. Active session hijacking is a broad category and is true at a high level, but the question asks for the type-and the specific technique described (TCP injection causing takeover) maps most directly to blind hijacking in CEH-style terminology.
Therefore, Sarah is demonstrating blind session hijacking.

Blowfish is the only option that matches all the technical characteristics described. In CEH cryptography concepts, symmetric algorithms are commonly distinguished by their structure (block cipher versus stream cipher), block size, and supported key lengths. The question states the algorithm encrypts data in 64-bit blocks and supports a variable key size ranging from 32 bits up to 448 bits, and it was introduced as a replacement for DES. Blowfish fits precisely: it is a symmetric block cipher with a 64-bit block size and a configurable key length from 32 to 448 bits, designed to be fast in software and positioned historically as an alternative to older ciphers such as DES.
The other choices do not align with these identifying properties. RC4 is a stream cipher and does not operate on fixed-size blocks, so it cannot match the 64-bit block requirement. AES is a block cipher but uses a 128-bit block size with fixed key sizes of 128, 192, or 256 bits, not 32 to 448 bits. Twofish, while related historically as a successor-era design, also uses a 128-bit block size and fixed key sizes up to 256 bits, so it does not match either.
From a CEH perspective, the mention of variable key sizes also hints at risk evaluation: shorter keys in any cipher can be brute-forced, so secure deployments require strong key length selection and proper key management. Additionally, Blowfish's 64-bit block size can be a concern in large-volume encryption scenarios due to block collision risks, which is why modern systems often prefer 128-bit block ciphers for new designs.

CEH identifies brute-force cryptanalysis as a method in which an attacker systematically tests every possible key, password, or passphrase until the correct one is found. When an attacker obtains initial bytes from an encrypted container-often referred to as known plaintext-they can use this to validate attempts as the tool iterates through candidate keys. Automated brute-force tools compare decrypted results with known header patterns, file signatures, or expected byte structures to determine when the correct key is reached. This process aligns precisely with brute-force password testing described in CEH cryptography modules. Quantum solving is not part of CEH scope, digest comparison relates to collision attacks, and analyzing output length pertains to padding oracle detection. The correct classification is automated brute-force cryptanalysis.

The central failure in the scenario is that a lost smartphone remained capable of accessing sensitive data, which means the organization lacked an effective lost device response control. In CEH-aligned mobile security guidance, one of the most important protections for lost or stolen devices is the ability to remotely secure the endpoint by locking it and wiping corporate data. This is typically implemented through Mobile Device Management tools and enterprise mobility controls. Registering devices with a remote locate and wipe facility ensures the security team can immediately take action once a device is reported missing, reducing the window in which an attacker can use stored sessions, cached credentials, saved tokens, or application access to reach protected resources such as patient records.
Option C is the best answer because it addresses both key needs implied by the incident: location capability to aid recovery and remote wipe to eliminate data exposure if recovery is uncertain. In healthcare environments, where protected health information is highly sensitive, CEH documentation emphasizes compensating controls that protect confidentiality when physical control of the device is lost. Remote wipe supports incident containment by preventing further access and limiting data disclosure.
Option B only provides tracking and does not guarantee data protection if the device cannot be recovered quickly. Option A helps protect data in transit on untrusted networks, but it does not solve the risk of a stolen device already authenticated to internal systems. Option D can help overall hygiene, but antivirus and DLP do not reliably stop misuse of a legitimately authenticated, lost device. Remote locate and wipe is the most direct mitigation for this exact gap.