In computer security terminology, which type of malicious program typically uses a spawn mechanism to create copies of itself and spread across systems or networks?

Introduction / Context:
This question is from the field of computer security and malware classification. Different types of malicious software behave in distinct ways. Understanding how they replicate and spread is essential for system administrators, developers, and students preparing for IT related exams. The term spawn mechanism refers to the ability of a program to create new copies or processes of itself, often without user intervention, which is a key characteristic of certain malware types.

Given Data / Assumptions:
The question asks which malware uses the spawn mechanism to duplicate itself and lists four options:
- Trojan horse
- Worm
- Keystroke logger
- Logic bomb
It is assumed that the learner has a basic understanding of how these malware categories differ in behaviour, particularly in terms of self replication and spreading through networks.

Concept / Approach:
A computer worm is a self replicating program that can duplicate itself and spread to other systems, often by exploiting network vulnerabilities or email attachments. Worms do not always require user action to propagate and frequently use mechanisms similar to spawning new processes or instances. A Trojan horse, by contrast, hides malicious code inside an apparently useful program but does not typically replicate itself. A keystroke logger records keystrokes to steal information, and a logic bomb is code that activates when certain conditions are met. These do not primarily rely on a spawn mechanism for self replication. Therefore, the correct answer is worm.

Step-by-Step Solution:
Step 1: Recall that a worm is defined as a self replicating malware program that can spread across systems and networks without user intervention. Step 2: Understand that worms often create multiple copies of themselves using process spawning, network connections, and other automated techniques. Step 3: Note that a Trojan horse is primarily about disguise and does not generally replicate on its own but instead relies on user installation. Step 4: Recognise that keystroke loggers and logic bombs are more about payload and triggering conditions than about replication. Step 5: Conclude that among the listed options, only the worm clearly matches the description of using a spawn mechanism to duplicate itself.

Verification / Alternative check:
One way to verify is to recall well known historical incidents. Famous examples like the Morris worm or e mail based worms spread rapidly by creating new instances on vulnerable machines. Textbooks on information security repeatedly stress that worms are self contained programs whose distinguishing feature is their ability to replicate and distribute themselves. Trojans, keyloggers, and logic bombs may be components inside other malware packages but are not defined primarily by self replication. This consistent emphasis supports the conclusion that the spawn based duplication behaviour belongs to worms.

Why Other Options Are Wrong:
Trojan horse: Designed to appear harmless or useful while hiding malicious functionality, but not fundamentally characterised by self replication.
Keystroke logger: Records keystrokes to capture passwords and sensitive data; it may be installed by other malware but does not typically spawn multiple copies of itself as a main feature.
Logic bomb: Malicious code that activates when certain logical conditions are met, such as a date or system event, but again not focused on replication.

Common Pitfalls:
A common mistake is to assume that all malware spreads in the same way and to confuse worms with Trojans or viruses. Another pitfall is to think that a Trojan horse that installs additional components is using a spawn mechanism in the same sense, but the primary definition of a worm emphasises automatic self replication. To avoid confusion, remember that worms are self replicating and network aware, while Trojans and other malware categories focus on different aspects such as disguise, logging, or delayed activation.

Final Answer:
The malware type that typically uses a spawn mechanism to duplicate itself and spread is the worm.