Hackers Are Turning Linux's eBPF Engine Into an "Invisible" Rootkit

CYBERDUDEBIVASH • ThreatWire

Published: October 17, 2025

Hackers Are Turning Linux’s eBPF Engine Into an “Invisible” Rootkit

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Image: Tux the Linux mascot (Wikimedia Commons)

TL;DR: Attackers are abusing eBPF (extended Berkeley Packet Filter) to load stealthy kernel hooks that hide processes, sockets, and files, intercept credentials, and tamper with telemetry—without dropping a traditional kernel module. If eBPF loading isn’t locked down, a single privileged process can implant a near-invisible rootkit. Lock eBPF to signed policies, restrict CAP_BPF/CAP_SYS_ADMIN, enable LSMs (SELinux/AppArmor), and monitor /sys + pinned maps for anomalies.

What is eBPF, and why attackers love it

eBPF lets the OS run small, verified programs inside the kernel to observe and safely modify behavior—networking, syscalls, tracing, even security policy. It’s a defensive superpower (think modern XDP firewalls, observability, zero-copy telemetry) but, in hostile hands, the same hooks can cloak malware, block detection, and rewrite events before your EDR ever sees them.

Typical attack chain (real-world playbook)

1. Initial foothold: weak SSH creds, vulnerable web app, or supply-chain script.
2. Privilege escalation: kernel/driver bug, misconfig (sudo NOPASSWD), or container breakout.
3. eBPF deployment: attacker loads BPF bytecode via bpf() syscalls; pins maps/programs under /sys/fs/bpf.
4. Stealth hooks: kprobes/tracepoints uprobes to hide processes/ports, filter packets, and scrub logs.
5. Persistence: services or cron that auto-re-pins programs at boot; masquerade as observability agents.

What an eBPF rootkit can do

• Process & file hiding: Filtered directory reads and procfs queries.
• Socket cloaking: Suppress specific ports from ss/netstat.
• Credential theft: Hook read/write or TLS libraries via uprobes to skim secrets.
• EDR blindspots: Tamper with audit/syscall events; drop packets before IDS sees them.
• Resilience: Pinned maps/programs survive process death; re-attachment on restart.

Who is most at risk?

• Kubernetes clusters with CNI plugins and observability stacks that already use eBPF.
• DevOps/SRE boxes where CAP_SYS_ADMIN is common and signing/enforcement is lax.
• Telco/edge and cloud gateways using XDP/TC for performance tuning.

Detection: how to spot an “invisible” eBPF implant

• List loaded programs/maps:

  bpftool prog show
  bpftool map show
  ls -al /sys/fs/bpf
  mount | grep bpf   # unexpected mounts?

• Look for suspicious pins (odd names, unexpected owners), non-root namespaces mounting BPF, or BPF objects owned by service accounts.
• Audit BPF syscalls:

  auditctl -a always,exit -F arch=b64 -S bpf -k bpf-load
  ausearch -k bpf-load

• Correlate with process ancestry (who invoked bpf()?) and recent privilege escalations.

Hardening checklist (immediate actions)

• Restrict capabilities: Drop CAP_BPF and CAP_SYS_ADMIN in containers and systemd services by default.
• Enable LSM enforcement: SELinux enforcing or AppArmor profiles that block unapproved BPF loads.
• Lock down BPF FS: Limit access to /sys/fs/bpf; disable unneeded BPF features on hardened hosts.
• Signed eBPF programs only: Use a loader that verifies signatures; maintain an allow-list of approved BPF object hashes.
• Kubernetes: PSP/OPA/Gatekeeper constraints to ban privileged pods and cap dangerous capabilities; review CNI/eBPF agents.
• Monitoring: Ship regular bpftool inventories; alert on new pins, new mounts, or changes to BPF maps.

Incident response: if you suspect BPF-based stealth

1. Isolate the node (cordon/drain in K8s, detach from load balancers).
2. Snapshot BPF state:

   bpftool prog dump xlated id <ID>
   bpftool map dump id <ID>

3. Unpin and detach unknown programs; reboot if hooks re-attach.
4. Rotate credentials touched by the host; redeploy from trusted images.

Related on CyberDudeBivash

• Linux hardening & kernel threats
• Kubernetes attacks & defenses
• Rootkits & stealth malware

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