Network security devices – UGC NET Question

Statements A, B and D correctly characterise typical roles of firewalls and IDS in network security, whereas C is an unrealistic claim. Firewalls enforce access control policies and IDS tools generate alerts, but no single device can guarantee perfect security. Defence-in-depth recognises the need for multiple layers of protection, procedures and monitoring. Consequently, the combination that includes A, B and D but not C is the only accurate choice.

Option A:
Option A is incomplete because it lists only A and B and omits D. Without mentioning defence-in-depth, one might wrongly assume that firewalls and IDS alone are sufficient, ignoring the multi-layered strategies recommended in practice.

Option B:
Option B is incorrect because it includes A, B and C and thereby accepts C. The assertion that a firewall always guarantees safety ignores new threats, misconfigurations and insider risks, so this combination cannot be accepted.

Option C:
Option C is correct because it captures the complementary functions of firewalls and IDS and acknowledges that they must be part of a broader security architecture. By excluding C, it rejects the mistaken belief in absolute protection through a single device.

Option D:
Option D is incomplete because it groups B and D only and leaves out A. Statement A provides the basic definition of what a firewall does, and its omission makes the combination conceptually incomplete.