# What is Stateless Packet Filtering?

> Stateless packet filtering permits or denies each packet independently according to a ruleset, without maintaining a table that relates it to an established flow.

- Canonical URL: https://yellowcube.eu/glossary/stateless-packet-filtering/
- Publisher: Yellow Cube
- Language: en
- Contact: hello@yellowcube.eu

## Content

Rules commonly use source and destination addresses, protocol numbers, transport ports, interfaces, direction, and selected header fields. Routers, switches, hosts, cloud controls, and firewalls can provide this function.

Because no connection history is consulted, return traffic must match its own explicit rule. This can make policy predictable and resource-efficient for simple flows, but protocols with dynamic ports, fragments, asymmetric behavior, or complex request-and-response patterns require careful handling. Implementations differ in rule order, default action, logging, and the fields available for matching.

### Key points

- **Rule design:** Start with required flows, use narrow sources, destinations, protocols, ports, and directions, define the default action, and document rule ownership and purpose.
- **Packet handling:** Specify IPv4 and IPv6 behavior, fragments, options or extension headers, spoofed source controls, ingress and egress policy, and malformed packets.
- **Operations:** Test allowed and denied paths, review counters and logs, remove obsolete or shadowed rules, and assess performance under high packet rates rather than assuming efficiency removes resource limits.
- **Important limitation:** A packet can satisfy every header rule and still carry an attack. Stateless filtering cannot determine whether it belongs to a legitimate prior exchange, and broad return-path rules can expose services unexpectedly.

### Related terms

[Firewall](<https://yellowcube.eu/glossary/firewall/>) · [Stateful firewall](<https://yellowcube.eu/glossary/stateful-firewall/>) · [Network access control list (ACL)](<https://yellowcube.eu/glossary/network-access-control-list/>) · [Network traffic](<https://yellowcube.eu/glossary/network-traffic/>) · [TCP/IP protocol suite](<https://yellowcube.eu/glossary/tcp-ip-protocol-suite/>)

### Sources

[NIST glossary: Packet Filter](https://csrc.nist.gov/glossary/term/packet_filter) · [NIST SP 800-41 Rev. 1: Guidelines on Firewalls and Firewall Policy](https://csrc.nist.gov/pubs/sp/800/41/r1/final)

## Attribution and scope

This Markdown representation is generated from the same approved content records as the canonical HTML page. Cite the canonical URL above when referencing this material. Product and service descriptions are informational; confirm project-specific requirements with Yellow Cube.