port-mass-scan – Security skill for AI agents

Port Mass Scan Skill

High-speed port scanning methodology using RustScan for single hosts and Masscan for large IP ranges. RustScan provides 400x speedup over Nmap for 1000-port scans (3-10s vs 5-10min). Masscan handles /8 and /16 ranges that Nmap cannot. The ISP and government network examples below were from authorized infrastructure assessments with signed RoE.

When to Use

• Authorized red team engagement with signed RoE covering the target IP range.
• Fast single-host port discovery before Nmap service enumeration.
• After subdomain-enumeration — scan resolved IPs for non-HTTP services.
• ISP-wide or /8 scanning without explicit written authorization is illegal in most jurisdictions. This skill exists for legitimate authorized engagements, not mass scanning.

Prerequisites

• terminal with masscan, rustscan, and nmap installed.
• For Masscan: root access (uses raw sockets), libpcap.
• For RustScan: nmap must be installed (for service enumeration pass-through).

How to Run

# Single host — RustScan (3-10 seconds for 1000 ports)
rustscan -a TARGET -r 1-65535 -- -sV

# /24 range — Masscan (2-5 minutes)
masscan -p1-65535 --rate=10000 -iL targets.txt -oJ scan.json

# /8 range — Masscan with banner grab (hours)
masscan -p80,443,8080,8443,22,3306,6379 --rate=50000 --banners -iL /8_range.txt -oJ scan.json

Quick Reference

| Scenario | Tool | Command | Time |

|----------|------|---------|------|

| Single host, all ports | RustScan | rustscan -a IP -r 1-65535 | 3-10s |

| /24 range, common ports | Masscan | masscan -p1-1000 --rate=10000 -iL /24.txt | 2-5 min |

| /16 range, web ports | Masscan | masscan -p80,443,8080,8443 --rate=50000 -iL /16.txt | 10-30 min |

| /8 camera hunt | Masscan | masscan -p554,80,8010 --rate=100000 -iL /8.txt | Hours |

| Banner grab (1 IP) | Masscan | masscan -p1-65535 --banners --source-ip ETH0_IP IP | 1-5 min |

Performance Comparison (empirical, 5000+ scans)

| Tool | 1000 ports (1 host) | /24 (1000 ports each) | /8 (web ports) | Accuracy |

|------|--------------------|-----------------------|-----------------|--------|

| Nmap | 5-10 min | ~30 min | Impossible (days) | 99% |

| RustScan | 3-10s | 15-30s | ~2 min | 98% (then Nmap -sV) |

| Masscan | 15-20s | 2-5 min | 30-60 min | 99% (TCP) |

Procedure

RustScan — Single Host Fast Discovery

TARGET="$1"
OUTDIR="$OUTDIR/ports"
mkdir -p "$OUTDIR"

echo "[*] RustScan: all 65535 ports on $TARGET"

# Fast scan + auto Nmap service detection
rustscan -a "$TARGET" -r 1-65535 -b 500 --accessible -- -sV -oN "$OUTDIR/${TARGET}_rustscan.nmap"

echo "[*] Open ports:"
grep 'open' "$OUTDIR/${TARGET}_rustscan.nmap" || echo "  None"

# For WAF/IDS evasion: slower batch size
rustscan -a "$TARGET" -r 1-65535 -b 100 -t 1500 -- -sV

Masscan — Large Range Scanning

RANGE_FILE="$1"      # One IP or CIDR per line
OUTDIR="$OUTDIR/ports"
mkdir -p "$OUTDIR"

# Step 1: Fast common ports scan
echo "[*] Masscan: common ports on $(wc -l < "$RANGE_FILE") targets"
masscan -p80,443,22,3306,6379,27017,8080,8443,554,21,25,5432,3389 \
  --rate=10000 -iL "$RANGE_FILE" -oJ "$OUTDIR/masscan_common.json" --wait=10

# Step 2: Full port scan on targets with hits
grep -Eo '"ip":"[^"]+"' "$OUTDIR/masscan_common.json" | sort -u | \
  sed 's/"ip":"//;s/"//' > "$OUTDIR/hits.txt"

echo "[*] Full scan on $(wc -l < "$OUTDIR/hits.txt") targets with open ports"
masscan -p1-65535 --rate=5000 -iL "$OUTDIR/hits.txt" \
  -oJ "$OUTDIR/masscan_full.json" --wait=30

Masscan — Banner Grabbing (service identification)

TARGET="$1"
OUTDIR="$OUTDIR/ports"

# Banner grabbing requires a separate IP for the TCP handshake
SOURCE_IP=$(hostname -I | awk '{print $1}')
echo "[*] Masscan banner grab from source IP: $SOURCE_IP"

masscan -p1-10000 --rate=5000 --banners --source-ip "$SOURCE_IP" \
  "$TARGET" -oJ "$OUTDIR/${TARGET}_banners.json"

# Alternative: two-phase (Masscan ports → Nmap services)
masscan -p1-65535 --rate=10000 "$TARGET" -oG "$OUTDIR/${TARGET}_grepable.txt" --wait=10
OPEN_PORTS=$(grep -Eo 'Host: \S+ \(\)\s+Ports:\s+\K[^#]+' "$OUTDIR/${TARGET}_grepable.txt" | \
  grep -Eo '\d+/open' | cut -d/ -f1 | tr '\n' ',' | sed 's/,$//')

if [[ -n "$OPEN_PORTS" ]]; then
  echo "[*] Nmap service detection on ports: $OPEN_PORTS"
  nmap -sV -p "$OPEN_PORTS" "$TARGET" -oN "$OUTDIR/${TARGET}_services.nmap"
fi

Masscan — IP Camera Hunting (RTSP port 554)

# Scan Brazilian ISP ranges for cameras (from Vivo, Claro, Oi)
echo "[*] Camera hunt on Claro 3G/4G ranges"
masscan -p554,80,8010,8011 --rate=50000 \
  --range [REDACTED_IP]-[REDACTED_IP] -oJ cameras_claro.json

echo "[*] Camera hunt on Vivo ranges"
masscan -p554,80,8010,8011 --rate=50000 \
  --range [REDACTED_IP]-[REDACTED_IP] -oJ cameras_vivo.json

# Post-process: probe discovered cameras for snapshots
grep -Eo '"ip":"[^"]+"' cameras_*.json | sed 's/"ip":"//;s/"//' | sort -u | \
while read ip; do
  # Axis camera snapshot
  code=$(curl -sk -o /dev/null -w "%{http_code}" --max-time 3 --connect-timeout 3 "http://$ip:8010/axis-cgi/jpg/image.cgi")
  [[ "$code" == "200" ]] && echo "[CAMERA] Axis: $ip:8010"
  # Generic RTSP
  code=$(curl -sk -o /dev/null -w "%{http_code}" --max-time 3 --connect-timeout 3 "http://$ip:554/")
  [[ "$code" != "000" ]] && echo "[RTSP] $ip:554"
  sleep 0.3
done

Sharding — Distribute Across N Machines

# On machine 1 (shard 1/4):
masscan -p1-65535 --rate=50000 --shard 1/4 -iL /8_range.txt -oJ shard1.json

# On machine 2 (shard 2/4):
masscan -p1-65535 --rate=50000 --shard 2/4 -iL /8_range.txt -oJ shard2.json

# On machine 3 (shard 3/4):
masscan -p1-65535 --rate=50000 --shard 3/4 -iL /8_range.txt -oJ shard3.json

# On machine 4 (shard 4/4):
masscan -p1-65535 --rate=50000 --shard 4/4 -iL /8_range.txt -oJ shard4.json

# Merge results
cat shard*.json | jq -s '.[]' > merged.json

Pitfalls

• Masscan requires root. Uses raw sockets. Run as root or with sudo.
• Rate > 100k may trigger IDS/IPS. Use --rate=50000 or lower for stealth. Use -T4 equivalent by setting appropriate --rate.
• Banner grabbing kills connections. Without --source-ip, Masscan must complete a full TCP handshake which tears down the connection. Use the two-phase approach (Masscan ports → Nmap services) for reliable service detection.
• UDP scanning is experimental. Masscan UDP support is limited. Use Nmap -sU for UDP.
• Ctrl+C auto-saves. Masscan saves progress on interrupt. Resume with --resume paused.conf.
• --excludefile is critical. Always exclude your own IPs and RFC 1918 ranges to avoid scanning yourself.

Verification

• RustScan: open ports must be confirmed with Nmap -sV for service version.
• Masscan: results must be deduplicated (Masscan may report same port multiple times from retransmissions).
• Banner grab: service versions must match between Masscan banners and Nmap probes.
• All open TCP ports must have a corresponding service identified (no "unknown" ports).