This isn’t your typical “What is eBPF?” tutorial. The internet is already drowning in those - complete with the same networking packet filtering examples and basic syscall tracing demos. Instead, we’re diving straight into the deep end: security-focused eBPF programming that actually matters in the real world.

You know that feeling when you’re monitoring your systems and something fishy is happening, but your security tools are about as useful as a chocolate teapot? Welcome to the club. Traditional security monitoring is like trying to catch a ninja with a butterfly net - theoretically possible, but practically hilarious.

Enter eBPF. If traditional monitoring tools are Hawkeye in Avengers, eBPF is Thor in Infinity war.

eBPF: The Security Game Changer (Finally, Some Real Talk) Link to heading

Before we get our hands dirty, let’s understand what makes eBPF revolutionary for security. eBPF (extended Berkeley Packet Filter) is a kernel technology that lets you run sandboxed programs in kernel space without changing kernel source code or loading kernel modules.

Think of the Linux kernel as a nightclub with the world’s strictest bouncer. Traditionally, if you wanted to monitor what’s happening inside, you had two options:

  1. Stand outside and guess (userspace monitoring)
  2. Become part of the security team (kernel modules)

eBPF is like getting a VIP pass that lets you observe everything happening inside while being completely safe and sandboxed.

The Security Superpowers eBPF Gives You Link to heading

Real-time, Zero-overhead Monitoring: eBPF programs run in kernel space, meaning they see every syscall, every network packet, every file operation as it happens. No polling, no delays, no “oops we missed that.”

Unbypassable Visibility: Malware can hide from userspace tools, disable logging daemons, or modify system utilities. But they can’t hide from eBPF because it sits below everything else in the stack.

Programmable Intelligence: Unlike static monitoring tools, eBPF programs can make decisions in real-time. Detect a suspicious pattern? Block it immediately. See an attack in progress? Collect detailed forensics automatically.

Production Safe: The eBPF verifier ensures your programs won’t crash the kernel. It’s like having a really paranoid code reviewer who never lets anything dangerous slip through.

eBPF Architecture: Under the Hood Link to heading

Let’s break down how eBPF actually works, because understanding the plumbing makes you a better security engineer:

┌─────────────────┐    ┌─────────────────┐
│   Userspace     │    │   Your Go/Python│
│   Application   │◄──►│   Program       │
└─────────────────┘    └─────────────────┘
         ▲                       ▲
         │                       │
    Maps │                       │ Events
         ▼                       ▼
┌─────────────────────────────────────────┐
│            Kernel Space                 │
│  ┌─────────────┐    ┌─────────────┐     │
│  │   eBPF      │    │   eBPF      │     │
│  │   Maps      │    │  Program    │     │
│  │             │    │             │     │
│  └─────────────┘    └─────────────┘     │
│         ▲                   ▲           │
│         └─────────┬─────────┘           │
│                   ▼                     │
│  ┌─────────────────────────────────┐    │
│  │     Hook Points                 │    │
│  │  • Syscalls (sys_enter_open)    │    │
│  │  • Tracepoints (sched_switch)   │    │
│  │  • Kprobes (security_file_open) │    │
│  │  • Network (XDP, tc)            │    │
│  └─────────────────────────────────┘    │
└─────────────────────────────────────────┘

Hook Points: These are where your eBPF programs attach to monitor events. For security, the most useful ones are:

  • Syscall tracepoints: Monitor system calls like execve, open, connect
  • Kprobes: Attach to any kernel function, including security subsystem functions
  • LSM hooks: Linux Security Module hooks for access control decisions

eBPF Programs: Your C code compiled to eBPF bytecode that runs in kernel space

eBPF Maps: Shared memory between kernel and userspace for data exchange

Verifier: The security bouncer that ensures your program is safe to run

What Makes eBPF Different (Spoiler: Everything) Link to heading

Remember the last time you tried to debug why your container mysteriously had root access to the host? Your traditional monitoring probably told you “something happened” with the enthusiasm of a Windows 95 error message. eBPF, on the other hand, is like having a security camera that records in 4K and can read lips.

Traditional Security Monitoring Problems:

  • Userspace blindness: Tools like ps, netstat, and lsof show you a snapshot, not the full movie
  • Easy to bypass: Attackers can kill monitoring processes, replace binaries, or use kernel-level rootkits
  • High overhead: Constantly polling for changes burns CPU and misses fast events
  • Limited context: You see the “what” but not the “how” or “why”

eBPF Security Monitoring Advantages:

  • Kernel level visibility: See everything, including what malware tries to hide
  • Real time processing: React to threats as they happen, not after
  • Rich context: Correlate events across processes, network, and file system
  • Efficient: Events are pushed to you instead of polling

eBPF Security Fundamentals: The Building Blocks Link to heading

Now that you understand the “why,” let’s dive into the “how.” Every eBPF security program follows the same basic pattern:

1. Choose Your Hook Point Link to heading

This is where you decide what events to monitor. For security, these are your bread and butter:

// Monitor process execution (catch malware, backdoors)
SEC("tracepoint/syscalls/sys_enter_execve")

// Monitor file access (detect data exfiltration, config tampering)
SEC("tracepoint/syscalls/sys_enter_openat")  

// Monitor network connections (C2 communication, lateral movement)
SEC("tracepoint/syscalls/sys_enter_connect")

// Monitor privilege escalation attempts
SEC("tracepoint/syscalls/sys_enter_setuid")

// Monitor namespace operations (container escapes)
SEC("tracepoint/syscalls/sys_enter_unshare")

2. Extract and Filter Events Link to heading

Raw syscall events are like drinking from a fire hose. You need to filter for what matters:

SEC("tracepoint/syscalls/sys_enter_execve")
int trace_execve(struct trace_event_raw_sys_enter* ctx) {
    char filename[256];
    char comm[16];
    
    // Get the command being executed
    bpf_probe_read_user_str(&filename, sizeof(filename), 
                           (void *)ctx->args[0]);
    
    // Get current process name
    bpf_get_current_comm(&comm, sizeof(comm));
    
    // Filter for suspicious patterns, should implement threat detection logic based on the requirements
    if (is_suspicious_exec(filename, comm)) {
        // Send alert to userspace
        send_security_event(ctx, filename, comm);
    }
    
    return 0;
}

3. Context is the King Link to heading

Security is all about context. When something suspicious happens, you need the full story:

struct security_event {
    u32 pid;
    u32 ppid;
    u32 uid;
    u32 gid;
    u64 timestamp;
    char comm[16];
    char filename[256];
    char cmdline[512];
    u32 container_id;  // For container security
};

// Collect rich context for security analysis
static void collect_process_context(struct security_event *event) {
    u64 pid_tgid = bpf_get_current_pid_tgid();
    event->pid = pid_tgid >> 32;
    event->timestamp = bpf_ktime_get_ns();
    
    u64 uid_gid = bpf_get_current_uid_gid();
    event->uid = uid_gid & 0xFFFFFFFF;
    event->gid = uid_gid >> 32;
    
    bpf_get_current_comm(&event->comm, sizeof(event->comm));
    
    // Get parent PID for process tree analysis
    struct task_struct *task = (struct task_struct *)bpf_get_current_task();
    if (task) {
        struct task_struct *parent = BPF_CORE_READ(task, parent);
        if (parent) {
            event->ppid = BPF_CORE_READ(parent, pid);
        }
    }
}

4. Real time Decision Making Link to heading

The power of eBPF is making security decisions at the speed of the kernel:

// Security policy enforcement in real-time
SEC("lsm/file_open")
int enforce_file_access(struct file *file) {
    struct dentry *dentry = BPF_CORE_READ(file, f_path.dentry);
    char filename[256];
    
    bpf_d_path(&file->f_path, filename, sizeof(filename));
    
    // Block access to sensitive files
    if (bpf_strstr(filename, "/etc/shadow") ||
        bpf_strstr(filename, "/root/.ssh/")) {
        
        u32 uid = bpf_get_current_uid_gid() & 0xFFFFFFFF;
        if (uid != 0) {  // Not root
            // Log the attempt
            log_security_violation(filename, uid);
            // Block the access
            return -EPERM;
        }
    }
    
    return 0;
}

Maps: Your Data Highway Link to heading

eBPF maps are the communication channels between your kernel programs and userspace applications. Think of them as a high speed pneumatic tube system in a bank, but instead of sending cash, you’re sending security alerts and data. Without maps, your eBPF program would be like a security guard who can see everything but has no way to report what they found, pretty useless for actually stopping attacks

Map Types for Security:

  • Hash Maps: Perfect for tracking state (process trees, network connections)
  • Ring Buffers: High-performance event streaming to userspace
  • Arrays: Configuration, counters, and statistics
  • LRU Hash: Automatic cleanup for long-running monitoring

eBPF Helpers: Your Kernel Toolkit Link to heading

eBPF helpers are pre built functions provided by the kernel that let your programs safely interact with kernel data structures. Think of them as a Swiss Army knife designed specifically for kernel programming, instead of figuring out how to safely access complex kernel internals, you get tested, verified functions that won’t crash your system. The kernel provides over 200 helper functions covering everything from memory operations to network processing, but for security monitoring, you’ll mostly use a core set of about 20-30 helpers that handle process information, file operations, and network data. It’s like having a curated toolkit where someone already figured out the safe way to do dangerous things.

Security-Specific eBPF Helpers (Your Greatest Hits):

  • bpf_get_current_uid_gid(): Who is running this process? (User and group IDs)
  • bpf_get_current_comm(): What’s the process name?
  • bpf_get_current_task(): Give me everything about this process
  • bpf_probe_read_user(): Safely read data from userspace (won’t crash if it’s garbage)
  • bpf_d_path(): What file path is being accessed?
  • bpf_ktime_get_ns(): When exactly did this happen? (Nanosecond precision)

The eBPF Security Toolkit: Choosing Your Weapon Link to heading

Before we dive into code, let’s talk about your options. It’s like choosing between a Swiss Army knife, a chainsaw, and an axe - they all cut things, but context matters.

BCC: The Training Wheels That Actually Work Link to heading

BCC (BPF Compiler Collection) is like Python for eBPF, it handles the ugly stuff so you can focus on the logic. Perfect for rapid prototyping and I need this working yesterday scenarios.

libbpf: The Grown-Up Option Link to heading

libbpf is like graduating from automatic to manual transmission. More control, better performance, but you need to know what you’re doing. This is where the adults play.

bpftrace: The Swiss Army Knife Link to heading

bpftrace is perfect for one-liners and quick investigations. It’s the awk of eBPF - deceptively simple but surprisingly powerful.

# One line to rule them all
bpftrace -e 'tracepoint:syscalls:sys_enter_execve { printf("Exec: %s\n", str(args->filename)); }'

The Bottom Line Link to heading

eBPF isn’t just another monitoring tool, it’s a paradigm shift. It’s the difference between watching security footage after a break-in and having a security guard who can see through walls and predict the future.

Your traditional monitoring tools are still useful, like a trusty flip phone. But when you need to catch modern threats, you need modern tools. And eBPF is about as modern as it gets without requiring a time machine.

Next up: “Building a Container Escape Detective with libbpfgo” where we’ll build something that would make Sherlock Holmes jealous.