Modern Port Scanning Techniques in 2026 (Rust Edition)

Modern port scanning is fast and stealthy. Build a safe, local Rust scanner that supports burst and low-and-slow modes, validate it, and learn what defenders watch for.

What You’ll Build

Two local open ports for testing (Python HTTP servers).
A Rust TCP connect scanner with concurrency, jitter, and burst/slow modes.
Validation steps and defensive signals to monitor.

Prerequisites

macOS or Linux with Rust 1.80+.
Python 3.10+.
Stay on localhost; do not scan external hosts without written approval.

Safety and Legal

Only scan assets you own or are authorized to test.
Keep concurrency low; stop on IDS/IPS complaints.
Tag your UA/traffic when moving beyond localhost.

Step 1) Start safe test targets

Click to view commands

python3 -m http.server 8100 > /tmp/http-8100.log 2>&1 &
python3 -m http.server 8101 > /tmp/http-8101.log 2>&1 &

Validation: `curl -I http://127.0.0.1:8100/` returns `200 OK`.

Step 2) Create the Rust project

Click to view commands

cargo new rust-portscan
cd rust-portscan

Validation: `ls` shows `Cargo.toml` and `src/main.rs`.

Step 3) Add dependencies

Replace Cargo.toml with:

Click to view toml code

[package]
name = "rust-portscan"
version = "0.1.0"
edition = "2021"

[dependencies]
tokio = { version = "1.40", features = ["full"] }
clap = { version = "4.5", features = ["derive"] }
futures = "0.3"
rand = "0.8"
anyhow = "1.0"

Validation: `cargo check` should pass after adding the code.

Step 4) Implement burst + low-and-slow scanning

Replace src/main.rs with:

Click to view Rust code

use clap::Parser;
use futures::stream::{self, StreamExt};
use rand::{seq::SliceRandom, thread_rng};
use std::net::SocketAddr;
use std::time::Duration;
use tokio::net::TcpStream;
use tokio::time::{sleep, timeout};

#[derive(Parser, Debug)]
#[command(author, version, about)]
struct Args {
    /// Host to scan (e.g., 127.0.0.1)
    #[arg(long)]
    host: String,
    /// Ports to scan, comma-separated
    #[arg(long, default_value = "22,80,443,8100,8101,9000")]
    ports: String,
    /// Max concurrent sockets
    #[arg(long, default_value_t = 50)]
    concurrency: usize,
    /// Delay between tasks in ms (low-and-slow)
    #[arg(long, default_value_t = 0)]
    delay_ms: u64,
    /// Per-connection timeout ms
    #[arg(long, default_value_t = 800)]
    timeout_ms: u64,
    /// Shuffle ports to reduce patterning
    #[arg(long, default_value_t = true)]
    shuffle: bool,
}

async fn is_open(host: &str, port: u16, timeout_ms: u64) -> bool {
    let addr: SocketAddr = format!("{host}:{port}").parse().unwrap();
    timeout(Duration::from_millis(timeout_ms), TcpStream::connect(addr))
        .await
        .is_ok()
}

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let args = Args::parse();
    let mut ports: Vec<u16> = args
        .ports
        .split(',')
        .filter_map(|p| p.trim().parse().ok())
        .collect();

    if args.shuffle {
        ports.shuffle(&mut thread_rng());
    }

    let results: Vec<(u16, bool)> = stream::iter(ports)
        .map(|port| {
            let host = args.host.clone();
            async move {
                let open = is_open(&host, port, args.timeout_ms).await;
                if args.delay_ms > 0 {
                    sleep(Duration::from_millis(args.delay_ms)).await;
                }
                (port, open)
            }
        })
        .buffer_unordered(args.concurrency)
        .collect()
        .await;

    for (port, open) in results {
        if open {
            println!("OPEN {}", port);
        }
    }
    Ok(())
}

Step 5) Run burst vs low-and-slow

Burst (faster, noisier):

Click to view commands

cargo run --release -- --host 127.0.0.1 --ports 22,80,443,8100,8101,9000 --concurrency 100 --delay-ms 0

- Low-and-slow (stealthier):

Click to view commands

cargo run --release -- --host 127.0.0.1 --ports 22,80,443,8100,8101,9000 --concurrency 5 --delay-ms 150

Expected: Ports 8100 and 8101 show as OPEN; others likely closed.

Validation: Output includes OPEN 8100 and OPEN 8101. If not, ensure the Python servers are running and timeouts are ≥800 ms.

Common fixes:

connection refused on all ports: check target host/port list.
Slow runs: reduce concurrency only after confirming the network is healthy.

Defender signals to monitor

Fan-out: count distinct ports touched per source in short windows.
Timing: bursts with zero delay are easy to spot; random jitter reduces signature but still shows elevated fan-out.
Honeypot ports: add canary ports to detect scans quickly.

Cleanup

Click to view commands

cd ..
pkill -f "http.server 8100" || true
pkill -f "http.server 8101" || true
rm -rf rust-portscan

Validation: `lsof -i :8100` and `:8101` should show no listeners.

Quick Reference

Burst for speed, low-and-slow for stealth—both must stay in authorized scope.
Shuffle ports and cap concurrency; add jitter to avoid easy pattern detection.
Defenders watch port fan-out and timing more than raw volume.

Learn in Public unlocks on Jan 1, 2026

Modern Port Scanning Techniques in 2026 (Rust Edition)

What You’ll Build

Prerequisites

Safety and Legal

Step 1) Start safe test targets

Step 2) Create the Rust project

Step 3) Add dependencies

Step 4) Implement burst + low-and-slow scanning

Step 5) Run burst vs low-and-slow

Defender signals to monitor

Cleanup

Quick Reference

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