A push and ACK flood is a network traffic attack that overwhelms a system with repeated push or acknowledgment messages, exhausting bandwidth, connection state, or processing capacity. In security operations, it can mask malicious activity, disrupt availability, and stress endpoints, load balancers, or authentication services that rely on constant session signaling.
What a Push and ACK Flood Does
A push and ACK flood is a volumetric and state-exhaustion attack pattern, not a protocol bug in isolation. The attacker’s goal is to force the target to spend bandwidth, memory, socket state, or CPU on repeated signaling until legitimate traffic is slowed or dropped.
This matters because the traffic itself can look superficially normal at the packet level, especially when the flood is made of small control messages rather than obviously malformed payloads. In practice, the security issue is the pressure it places on connection tracking, session handling, and any service that assumes a steady rhythm of acknowledgments or pushes.
Why It Disrupts Availability
Availability failures happen when a system cannot keep enough resources free to complete useful work. A push and ACK flood can consume those resources in a few different ways: it can fill bandwidth, inflate connection tables, trigger retransmission churn, or keep application workers busy processing meaningless state transitions.
Systems with shared front ends, reverse proxies, or load balancers are especially exposed when the flood reaches the edge and propagates inward. Even if the origin service is not fully saturated, upstream components may become the bottleneck and make the whole service look unavailable.
How It Interferes with Security Operations
Operators care about this attack because it can create noise that hides other activity. A sustained flood can bury logs, distort baselines, and make it harder to distinguish normal user behavior from malicious follow-on actions.
It can also stress supporting services that enforce trust decisions, including authentication gateways and session-dependent controls. When those components are overloaded, defenders may see delayed logins, failed token validation, or incomplete telemetry, which reduces confidence in the environment’s security picture.
What Defenders Should Verify
Exposure starts with understanding where the protocol or signaling path is reachable and which assets depend on it. Teams should confirm whether the affected service is internet-facing, whether rate limiting exists at the edge, and whether upstream devices are likely to exhaust state before the protected application does.
Defenders should also review vendor guidance for the exact product and traffic pattern involved, because the practical mitigation often depends on where the state is tracked and which control plane is being pressured. Packet filtering alone is rarely sufficient if the bottleneck is connection state or application workers rather than raw bandwidth.
Risk and Threat Considerations
Push and ACK floods are dangerous because they weaponize a normal-looking traffic pattern to create denial of service and to conceal parallel activity. The operational risk is not just outage, but loss of visibility while the environment is under load.
Failure mechanism: Repeated signaling exhausts bandwidth, connection state, or worker capacity faster than the target can recover, while also degrading monitoring fidelity and downstream trust decisions.
Impact: Users experience timeouts and failed sessions, security teams lose clean telemetry, and adjacent services such as load balancers or authentication layers may fail in a cascading way.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP API Security Top 10 and MITRE ATT&CK address the attack and risk surface, while NIST CSF 2.0, NIST SP 800-53 Rev 5 and CIS Controls v8 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST CSF 2.0 | PR.AA-05 — Authenticator Management | Repeated session signaling can overload auth workflows that depend on stable verification state. |
| DE.CM-01 — Networks and network services are monitored | Flood traffic is primarily a network-service visibility and saturation problem. | |
| PR.PS-05 — Deployment Management | Edge and load-balancing deployments determine how much signaling pressure the service can absorb. | |
| Recommendation — Harden authentication paths so session signaling does not become a denial-of-service bottleneck. Monitor traffic and service-state anomalies to detect flooding before availability fails. Tune deployment controls and rate limits to absorb repeated signaling without collapsing service state. | ||
| NIST SP 800-53 Rev 5 | SC-5 — Denial of Service Protection | The term is a denial-of-service traffic pattern that exhausts bandwidth or processing capacity. |
| AU-6 — Audit Record Review, Analysis, and Reporting | Floods can mask malicious activity by degrading log quality and analyst visibility. | |
| Recommendation — Apply DoS protections at the network edge to limit flood-driven resource exhaustion. Correlate logs and alerts so flooding does not hide concurrent malicious activity. | ||
| CIS Controls v8 | CIS-13 — Network Monitoring and Defense | The attack is a network traffic abuse pattern that requires monitoring and throttling controls. |
| Recommendation — Use network defense controls to detect abnormal signaling rates and suppress flood traffic. | ||
| OWASP API Security Top 10 | API4 — Unrestricted Resource Consumption | The attack exhausts connection state and processing capacity through repeated requests or acknowledgments. |
| Recommendation — Limit resource consumption so repeated signaling cannot monopolize service capacity. | ||
| MITRE ATT&CK | T1498 — Network Denial of Service | Push and ACK flooding is a network-based denial-of-service technique. |
| Recommendation — Map flood indicators to T1498 and alert on sustained packet-rate or session-state abuse. | ||
Practitioner Guidance
Why practitioners should care: The right response is usually to reduce the amount of state the target must hold, not just to block packets. That means concentrating on edge controls, session resilience, and the parts of the stack most likely to fail first under repeated acknowledgments or pushes.
What to watch for: Watch for sudden growth in connection state, abnormal repetition of small control messages, rising retransmissions, and disproportionate CPU or memory pressure on front-end infrastructure. If the flood is persistent, compare edge logs with application logs to see where the saturation begins.