Linux: block outgoing traffic to specific ip or port using iptables or ufw

• Using iptables:

• # block outgoing traffic to ip 1.2.3.4
  iptables -A OUTPUT -d 1.2.3.4 -j DROP
  
  # block outgoing traffic to port 5678
  iptables -A OUTPUT -p tcp –dport 5678 -j DROP
  
  # block outgoing traffic to 1.2.3.4:5678
  iptables -A OUTPUT -p tcp -d 1.2.3.4 –dport 5678 -j DROP
  

• Using ufw:

• 
  # block outgoing traffic to ip 1.2.3.4
  ufw deny out to 1.2.3.4
   
  # block outgoing traffic to port 5678
  ufw deny out to any port 5678
  
  # block outgoing traffic to 1.2.3.4:5678
  ufw deny out to 1.2.3.4 port 5678
  

see also: Linux Iptables Block Outgoing Access To Selected or Specific IP Address / Port