Karp Linux Kernel Level Arp Hijacking Spoofing Utility Access

If you find an unexpected module, rmmod karp – but a real attacker will hide it via rootkit techniques. kArp demonstrates a simple truth: moving attacks from user space to kernel space increases reliability and evades kill‑‑9 . Red teams can use this to persist on compromised routers or jump hosts. Defenders must move beyond process monitoring to kernel integrity checks (e.g., tripwire for modules, IMA, or eBPF-based LSM hooks).

return NF_ACCEPT;

ip = ip_hdr(skb); if (!ip) return NF_ACCEPT; kArp Linux Kernel Level ARP Hijacking Spoofing Utility

Disclaimer: This post is for educational purposes and authorized security testing only. ARP spoofing is illegal without explicit permission from the network owner. Do not run this on networks you do not own or lack written authorization for. If you find an unexpected module, rmmod karp

// Mirror for gateway -> victim direction if (ip->daddr == gateway_ip) build_arp_reply(victim_ip, attacker_mac, gateway_ip, &spoof_arp); dev_queue_xmit(...); Defenders must move beyond process monitoring to kernel

static unsigned int karphook_post(void *priv, struct sk_buff *skb, const struct nf_hook_state *state)

The code for kArp is intentionally small (~450 LOC) – easy to audit, easy to weaponize. I’ll release it on GitHub under an educational license in the coming weeks. ARP spoofing is a 40-year-old attack, but it refuses to die. Until IPv6 with Secure Neighbor Discovery (SEND) is universal, and until every switch runs DAI, kernel-level ARP tricks will remain in every serious attacker’s toolkit.