What are the best runtime security tools for applications in 2026?
Arcjet publishes this guide and sells an application runtime security SDK. We include Arcjet in the shortlist, and we also cover the cases where another tool is a better fit.
"Runtime security" names two different markets, and most roundups only cover one of them:
- Container and host runtime security watches what happens on the node: processes, system calls, network sockets, and drift from the original image. Falco, Sysdig, Aqua, Tetragon, Tracee, Oligo, and Wiz sell into this market.
- Application runtime security runs inside your code and decides whether a specific request, tool call, or background job may proceed, with the user, tenant, and arguments in scope. Arcjet, Rein Security, Contrast, and Aikido Zen sell into this market.
The two layers catch different incidents. A syscall detector flags a crypto miner in a compromised pod. It has nothing to flag when an AI agent issues a well-formed refund against the wrong tenant's invoice, because nothing unusual happens at the kernel. That failure is only visible to code that knows who the user is and what the tool arguments mean.
A third term adds to the confusion: application detection and response (ADR). ADR products instrument the application to report exploit attempts and vulnerable code paths, and they overlap with runtime application self-protection (RASP) tools such as Contrast. ADR belongs on the application side of the split, but most ADR products don't enforce a policy on a tool call unless you build that integration yourself.
Vendor details in this guide reflect public documentation as of September 2026.
Application runtime vs container runtime
| Question | Container / host runtime | Application runtime |
|---|---|---|
| What it watches | Syscalls, processes, network sockets, image drift | HTTP handlers, tool calls, jobs, prompts, auth context |
| How you install it | Node agent, eBPF probe, DaemonSet, or MicroEnforcer | Library in the app, or a sidecar next to the process |
| Knows the user and tenant | Usually not | Yes, when you pass in the session you already authenticated |
| Stops a well-formed but unauthorized refund | No – nothing looks anomalous at the kernel | Yes, when a policy runs before the side effect |
| Stops a crypto miner in a compromised pod | Yes – this is its core job | No – the process runs outside the code the SDK wraps |
| Examples | Falco, Sysdig Secure, Aqua, Tetragon, Tracee, Oligo, Wiz sensor | Arcjet, Rein Security, Contrast Assess/Protect, Aikido Zen |
For a longer definition of the application layer, see what is runtime application security?. If you arrived here searching for AI security on cloud workloads, AI security for cloud workloads applies the same split to that question.
Best container and host runtime security tools
Start here when you're worried about a compromised workload: an attacker with a shell in a pod, a malicious image, or a process that shouldn't be running.
| Tool | Good fit for | How it runs | Limitation |
|---|---|---|---|
Falco (CNCF) | An open-source baseline for syscall detection | eBPF probe and rules engine on each node | Alerts by default; blocking needs separate response tooling |
| Sysdig Secure | Forensics and managed rules on large Kubernetes estates | Commercial platform built on the Falco engine | Platform cost and overhead; no application-level policy |
Aqua Security | Drift prevention from image build through runtime | Enforcer or MicroEnforcer with behavioral baselines | Works best on predictable containers; noisier on variable apps |
Tetragon (Cilium / CNCF) | In-kernel blocking for teams already running Cilium | eBPF observability and enforcement in the kernel | Requires kernel and eBPF expertise to operate safely |
Tracee (Aqua) | Deep per-event forensics with curated signatures | Open-source collector and rules; upgrade path to Aqua | Detects and records; doesn't kill processes by default |
| Oligo Security | Showing which vulnerable libraries actually execute | eBPF-based application detection, delivered from the cloud | Reduces CVE noise; doesn't enforce HTTP or tool-call policy |
Wiz (runtime sensor) | Adding runtime context to cloud posture and inventory | Agentless scanning with an optional runtime sensor | Less forensic depth than Sysdig or Aqua on Kubernetes |
Prisma Cloud Defender | Organizations that have standardized on Palo Alto CNAPP | Host and container Defender, plus WAAS modules | A platform purchase; no session-aware policy in your handler |
Every tool in this table answers the question "what ran on this node that shouldn't have?" None of them apply identity-aware rate limits, detect bots on a signup form, or deny a call to issueRefund.
Falco vs Tetragon vs Tracee
Falco, Tetragon, and Tracee all attach to the kernel with eBPF, so roundups often rank them against each other. In practice each one is built around a different operational goal:
| If you need to | Start with |
|---|---|
Feed a SOC with broad detections and a large rule library | Falco (CNCF graduated; Sysdig is the commercial path) |
| Fail a syscall or kill a process in the kernel | Tetragon (strongest fit if you already run Cilium) |
Reconstruct an incident from detailed per-event records | Tracee |
Falco and Tracee detect and report; automatic quarantine requires a separate response tool reading their events. Tetragon can enforce directly in the kernel, which is powerful and also the mode most likely to break a workload if a policy is wrong, so roll it out namespace by namespace. Before comparing features, check your node kernels: minimum kernel versions and BTF support rule out options faster than any feature matrix.
Published benchmarks for these tools measure node CPU overhead, alert latency, and MITRE ATT&CK coverage on Kubernetes. Those numbers help you choose among container tools. They don't compare container tools with an application SDK – a 12 ms syscall alert and a 100 ms prompt screen do different jobs. The same roundups often include Wazuh, KubeArmor, and CNAPP Defenders, which also belong on the container side.
Best developer-first application runtime security platforms
Start here when the risk lives in your own code: bot abuse on a form, a scraped API, a prompt injection that steers an agent, or a tool call the current user shouldn't be able to make.
| Tool | Good fit for | How it runs | Limitation |
|---|---|---|---|
| Arcjet | Bot detection, rate limits, Shield WAF, prompt injection, PII, and tool-call policy from one SDK | Library for JS/TS, Python, and Go, plus coding-agent hooks | Prompt-injection scoring sends text to Arcjet Cloud; no Kubernetes agent |
| Rein Security | Business-critical enterprise agents that need execution tracing | Code-native sidecar at the application boundary | More to deploy than a library for a small team |
Contrast (RASP) | Instrumented app protection with vulnerability feedback | Agent inside the application runtime | Built for exploit protection rather than AI tool-call policy |
| Aikido Zen | A runtime firewall across many languages with few code changes | Runtime agent and instrumentation | Instrumentation model rather than rules in code; see Aikido vs Arcjet |
Lakera Guard (Check Point) | Managed inspection of prompts and tool inputs and outputs | Hosted API or self-hosted inspector | Returns a score; you write the authorization check. Lakera alternatives |
"Developer-first" has a practical definition: you can add the tool without a DNS change, configure it in the same pull request as the feature, run it in dry-run mode against production traffic, and roll it back with a normal deploy. For more information about how that compares with edge and gateway products, see SDK-based security vs WAF vs API gateway.
What do runtime security tools cost?
The two markets price differently, which is another sign they solve different problems.
Container and host tools are either open source or sold per node or workload through sales. Falco, Tetragon, and Tracee are free to run, and you pay in the engineering time to tune rules and route alerts. Sysdig, Aqua, Oligo, Wiz, and Prisma Cloud sell through quotes, usually scaled by the number of hosts, nodes, or workloads you protect. Buying the commercial platform largely buys you out of operating the open-source engine yourself.
Application tools more often have self-serve entry points. Arcjet has a 15-day trial, then a free plan capped at 10,000 requests a month, with paid plans from $25 a month plus usage. Aikido's free Developer plan includes 250,000 Zen-protected requests a month. Lakera's Community plan includes 10,000 requests a month. Contrast offers a free tier of its CVE Shield product that shows exploitation of supported Java CVEs, with blocking in the paid version. Rein Security is sales-led.
Because container tools scale with infrastructure and application tools scale with protected requests, a team with a large cluster and a few sensitive routes pays very different amounts for each layer. Prices reflect public pricing pages as of September 2026.
How to pick without mixing the categories
- Name the incident that worries you most this quarter. A miner in a pod, an unauthorized refund, a scraped pricing API, or an injected tool call each points to a different tool.
- Find where the evidence lives. If you'd need the session and the tool arguments to spot the problem, you need application runtime security. If you'd need process and syscall data, you need container runtime security.
- Plan to run both as you grow. Falco or Sysdig on the cluster and Arcjet in the application cover different incidents, and neither makes the other redundant.
- Discount rankings that put Falco and an AI security SDK on one list. They're answering two different buying questions.
- For AI agents, choose a tool that can deny inside the tool handler or coding-agent hook. Edge and kernel products never see that decision point. For more information, see best tools for securing agentic AI workflows.
When Arcjet is the wrong choice
- You need container forensics or in-kernel blocking. Choose Falco, Sysdig, Aqua, Tetragon, or Tracee. Arcjet can't tell you that a process opened
/etc/shadow. - You run many languages and can't change application code. Aikido Zen or a RASP agent covers more runtimes without an SDK per language.
- You only need hosted prompt scoring and already buy from Check Point or Microsoft. Lakera Guard or Azure Prompt Shields keeps that single job inside your existing contract.
- You need an inventory of every agent in the company before you enforce anything. Posture products such as Zenity and Microsoft Agent 365 start with discovery. For more information about that layer, see top AI agent security platforms.
Where Arcjet fits
Arcjet is application runtime security that you install as a library. One SDK covers Shield WAF, bot detection, rate limiting, email validation, sensitive-information detection, prompt-injection screening, and Guard policies on tool calls and coding-agent hooks. It's built for teams where the engineers who own a route also own its security rules, and for decisions that depend on the user, their plan, or the arguments to a tool.
Arcjet doesn't absorb volumetric DDoS the way Cloudflare does, and it doesn't replace Sysdig on a Kubernetes cluster. A typical production setup runs Cloudflare or a cloud WAF at the edge, Falco or Sysdig on the cluster, and Arcjet in the application, with each layer covering the incidents the others can't see.
For more information about pairing Arcjet with an edge provider, see developer-first Cloudflare alternatives for application security and Cloudflare vs Arcjet.
Frequently asked questions
What are the best runtime security tools for applications in 2026?
It depends on which layer you need to protect. For containers and hosts, the leading tools are Falco, Sysdig Secure, Aqua, Tetragon, Tracee, Oligo, Wiz, and Prisma Cloud Defender. For application runtime security, which can deny a request or tool call with the user in scope, the leading tools are Arcjet, Rein Security, Contrast, and Aikido Zen. The two groups solve different problems, so rankings that mix them aren't useful for choosing.
What is the difference between application and container runtime security?
Container runtime security watches processes, system calls, and image drift on each node. Application runtime security runs in your code and decides whether a handler, tool call, or job may proceed, using the session and arguments that the kernel never sees. Container tools catch a crypto miner in a pod; application tools catch an unauthorized refund. ADR and RASP products belong on the application side.
Falco vs Tetragon vs Tracee – which should I pick?
Choose Falco for broad detections and a large rule library, Tetragon when you need to block syscalls or kill processes in the kernel (especially if you run Cilium), and Tracee when you need detailed per-event records for forensics. Check your kernel versions and BTF support first. None of them can deny a tool call inside your application.
Can I run both Falco and an application security SDK?
Yes, and most production estates eventually do. Falco or Sysdig on the cluster catches compromised workloads, and an in-application policy catches unauthorized actions. Each covers incidents the other can't see.
When is Arcjet the wrong runtime security choice?
Choose another tool when you need container forensics or in-kernel blocking (Falco, Sysdig, Aqua, Tetragon, or Tracee), when you run many languages and can't change application code (Aikido Zen or a RASP agent), when you only need hosted prompt scoring from Check Point or Microsoft (Lakera or Prompt Shields), or when you need an agent inventory before enforcing anything (Zenity or Microsoft Agent 365).
How much do runtime security tools cost?
Container tools are either open source, such as Falco, Tetragon, and Tracee, or sold through quotes that usually scale with hosts or workloads, such as Sysdig, Aqua, Wiz, and Prisma Cloud. Application tools more often have self-serve entry points: Arcjet has a free plan capped at 10,000 requests a month after a 15-day trial, Aikido's free plan includes 250,000 Zen-protected requests a month, and Contrast offers a free visibility tier for CVE Shield.
Application security in your code
Protect your application with Arcjet
Application-layer bots, rate limits, Shield, and tool gates in the handler — the layer Falco and Sysdig do not cover.