Petr Zak

Finance and IT enthusiast, problem solver

Category: IT Security

Must-Know Ports



 20, 21 FTP
 22 SSH
 23 Telnet
 25 SMTP
 42 WINS
 53 DNS
 80, 8080 HTTP
 88 Kerberos
 110 POP3
 111 Portmapper Linux
123 NTP
139 SMB
143 IMAP
161, 162 SNMP
389 LDAP
445 CIFS
514 Syslog
636 Secure LDAP


Network topologies

  • Bus – simple but vulnerable
  • Ring – simple, vulnerability can be handled by concentric design
  • Star – most common, resistance to outages, node failure does not cause the whole network to go down
  • Mesh – for mission critical services, high level of redundancy; Internet
  • Hybrid – mix of the above

Hacker’s workflow

Everyone has its own, but it usually consists of:

  • Footprinting (passive)
  • Scanning (active)
  • Enumeration – is there a value behind the door?
  • Hacking – attack execution
  • Covering – hiding the activity from previous steps
  • Backdoors – wanna come back?


We do not refer to the Central Intelligence Agency but key concepts in ethical hacking:

  • Confidentiality – keep the information away from non-authorized people/systems; using encryption, access rights
  • Integrity – keep the information unaltered by non-authorized
  • Availability – keep the information available to those who need it

Opposite would be:

  • Disclosure
  • Alteration
  • Disruption


Hacker’s needs…

Hacker’s needs to commit a crime are the same like in case of a regular crime:

  • Means
  • Motive
  • Opportunity


Ethical Hacker’s needs:

  • Good contract
  • Do only what you have permission to do
  • Confidentiality and privacy in mind

Boot Kali linux to console

Get the current session type, text-mode or graphical:

systemctl get-default

Set the current session type to text-mode by disabling gdm autostart:

systemctl set-default

Enable lightdm autostart:

systemctl set-default

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