Why are Trojans considered less harmful than viruses?

Trojans are considered less harmful than viruses primarily because they cannot propagate on their own. While both Trojans and viruses can cause damage to systems, the nature of how they spread is fundamentally different.

Trojans are deceptive software that tricks users into installing them, often masquerading as legitimate applications or files. They rely on social engineering or user interaction for installation, which means that they cannot replicate or spread to other systems independently. In contrast, viruses attach themselves to legitimate executables and can self-replicate, making them more capable of widespread damage once they infect a hosting system.

Understanding this key distinction helps to clarify why Trojans may be viewed as less of a threat in terms of contagion compared to viruses. Their harm often comes from the actions they perform after installation, such as stealing data or creating backdoors, rather than from their ability to spread across networks or systems unassisted.