eBPF-based Security

eBPF (extended Berkeley Packet Filter) is a revolutionary technology that allows running sandboxed programs in the Linux kernel without modifying kernel source code or loading kernel modules. For security, eBPF enables efficient, low-overhead monitoring and enforcement at the kernel level.

What is eBPF?

eBPF programs run in a virtual machine inside the Linux kernel, providing:

Low overhead - Minimal performance impact
Real-time monitoring - See events as they happen
Kernel-level visibility - Access to system calls, network packets, and more
Safety - Programs are verified before execution

Think of eBPF as a way to add custom security logic directly into the operating system kernel without the complexity and risk of kernel modules.

How eBPF Works

flowchart TD A[User Space] --> B[System Call/Event] B --> C[Linux Kernel] C --> D[eBPF Program] D --> E{Program Logic} E --> F[Action/Log] F --> G[User Space] style A fill:#e1f5ff style C fill:#fff4e1 style D fill:#e8f5e9 style F fill:#ffebee

eBPF for Security

eBPF enables several security use cases:

System Call Monitoring

Monitor all system calls made by containers:

SEC("tracepoint/syscalls/sys_enter_execve")
int trace_execve(struct trace_event_raw_sys_enter* ctx) {
    // Log process execution
    return 0;
}

Network Packet Inspection

Inspect network traffic in real-time:

SEC("xdp")
int xdp_prog(struct xdp_md *ctx) {
    // Inspect and filter network packets
    return XDP_PASS;
}

File System Monitoring

Track file access and modifications:

SEC("kprobe/vfs_write")
int kprobe_vfs_write(struct pt_regs *ctx) {
    // Monitor file writes
    return 0;
}

eBPF Security Tools

Cilium

Cilium uses eBPF for networking and security:

Network policy enforcement
Service mesh capabilities
Network observability
DDoS protection

Falco

Falco uses eBPF for runtime threat detection:

System call monitoring
Container behavior analysis
Real-time alerting

KubeArmor

KubeArmor uses eBPF for policy enforcement:

Process blocking
File system protection
Network restrictions

Tetragon

Isovalent’s Tetragon provides eBPF-based security observability:

Process execution monitoring
Network connection tracking
File system access logging
Kubernetes-aware policies

Advantages of eBPF

Performance

Low overhead - Minimal CPU and memory usage
Kernel-level efficiency - No context switching
Selective monitoring - Only monitor what you need

Safety

Verification - Programs are verified before execution
Sandboxed - Programs can’t crash the kernel
Type safety - Strong type checking

Flexibility

Dynamic loading - Load programs without rebooting
Hot-swappable - Update programs on the fly
No kernel modifications - Works with standard kernels

eBPF vs Traditional Approaches

Traditional Kernel Modules

Require kernel compilation
Can crash the kernel
Difficult to update
Require root access

eBPF Programs

Load dynamically
Verified for safety
Easy to update
Can run unprivileged (for some programs)

Practical Example: Network Monitoring

Here’s how eBPF can monitor network connections:

#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>

SEC("tracepoint/syscalls/sys_enter_connect")
int trace_connect(struct trace_event_raw_sys_enter* ctx) {
    struct sockaddr *addr = (struct sockaddr *)ctx->args[1];
    
    // Log connection attempts
    bpf_printk("Connection attempt detected\n");
    
    return 0;
}

Best Practices

Start with existing tools - Use Cilium, Falco, or KubeArmor before writing custom programs
Minimize overhead - Only monitor what’s necessary
Test thoroughly - eBPF programs run in the kernel
Use appropriate hooks - Choose the right kernel hook for your use case
Handle errors gracefully - Programs should fail safely
Monitor performance - Track eBPF program overhead

Limitations

Kernel version - Requires Linux 4.9+ (features vary by version)
Complexity - Writing eBPF programs requires kernel knowledge
Verification limits - Some programs may be rejected by the verifier
Resource limits - Programs have instruction and memory limits