In which layer of the OSI model do stateless packet filtering firewalls operate?

Stateless packet filtering firewalls operate at the network layer of the OSI model. This layer is responsible for the routing and forwarding of data packets across networks. Stateless firewalls analyze each packet individually without retaining any context or memory of previous packets. They make decisions based solely on information contained in the packet header, such as the source and destination IP addresses, as well as the protocol type (TCP, UDP, ICMP, etc.).

This functionality allows the network layer firewalls to process incoming and outgoing packets efficiently, determining whether to allow or block packets based solely on predefined rules. Unlike stateful firewalls, which maintain session information and can understand the state of the traffic, stateless firewalls do not perform this level of inspection and are primarily focused on basic filtering at the packet level.

In contrast, firewalls that were mentioned in the other layers operate on different principles and are designed for different types of processing and control. The application layer, for instance, handles application-specific data and may include more complex filtering mechanisms that focus on the details of the actual application protocols, rather than just the packet headers.