List the port number and service for each of the following: FTP, SSH, Telnet, SMTP, DNS, HTTP, POP3, HTTPS, MySQL, RDP.

Here's a summary of the essential port numbers and types of port scans:

Essential Port Numbers to Memorize

• Port 20/21:
  • Service: FTP (File Transfer Protocol)
  • Description: File upload/download (unencrypted)
  • Risk: HIGH
• Port 22:
  • Service: SSH (Secure Shell)
  • Description: Encrypted remote terminal access
  • Risk: MED
• Port 23:
  • Service: Telnet
  • Description: Unencrypted remote access, sends passwords in plaintext
  • Risk: CRIT
• Port 25:
  • Service: SMTP (Simple Mail Transfer Protocol)
  • Description: Outbound email
  • Risk: MED
• Port 53:
  • Service: DNS (Domain Name System)
  • Description: Name-to-IP resolution
  • Risk: MED
• Port 80:
  • Service: HTTP (Web traffic)
  • Description: Completely unencrypted
  • Risk: HIGH
• Port 110:
  • Service: POP3 (Email receiving)
  • Description: Often transmits credentials in plaintext
  • Risk: HIGH
• Port 443:
  • Service: HTTPS (Encrypted web traffic)
  • Description: TLS/SSL secured
  • Risk: LOW
• Port 3306:
  • Service: MySQL
  • Description: MySQL database, should NEVER be internet-facing
  • Risk: CRIT
• Port 3389:
  • Service: RDP (Remote Desktop Protocol)
  • Description: Windows remote access
  • Risk: CRIT

Types of Port Scans

• Flag: -sT
  • Scan Type: Connect Scan
  • Stealth: LOW
  • How it works: Completes the full TCP handshake. Most reliable but easily detected in server logs.
• Flag: -sS
  • Scan Type: SYN / Half-Open
  • Stealth: HIGH
  • How it works: Sends SYN, receives SYN/ACK but never completes with ACK. Fewer logs. Most common scan.
• Flag: -sF
  • Scan Type: FIN Scan
  • Stealth: HIGH
  • How it works: Sends FIN packet. Open ports ignore it; closed ports reply RST. Bypasses some firewalls.
• Flag: -sN
  • Scan Type: NULL Scan
  • Stealth: HIGH
  • How it works: Sends a packet with NO flags set. Very stealthy against older or non-standard systems.
• Flag: -sX
  • Scan Type: XMAS Scan
  • Stealth: HIGH
  • How it works: Sets FIN+PSH+URG flags simultaneously - 'lights up like a Christmas tree'. Very stealthy.
• Flag: -sA
  • Scan Type: ACK Scan
  • Stealth: MED
  • How it works: Maps firewall rules - does NOT identify open ports, but reveals filtered vs. unfiltered.
• Flag: -sI
  • Scan Type: Idle / Zombie
  • Stealth: MAX
  • How it works: Uses a third-party zombie machine's IP to probe target. Hides attacker identity completely.