Amarildo - IPTABLES

# Drop everything
iptables -P OUTPUT  DROP
iptables -P INPUT   DROP
iptables -P FORWARD DROP

# drop TCP sessions opened prior firewall restart
iptables -A INPUT -p tcp -m tcp ! --tcp-flags SYN,RST,ACK SYN -m state --state NEW -j DROP
iptables -A OUTPUT  -p tcp -m tcp ! --tcp-flags SYN,RST,ACK SYN -m state --state NEW -j DROP

# drop packets that do not match any valid state and log them
iptables -N drop_invalid
iptables -A OUTPUT   -m state --state INVALID  -j drop_invalid
iptables -A INPUT    -m state --state INVALID  -j drop_invalid
iptables -A INPUT -p tcp -m tcp --sport 1:65535 --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j drop_invalid
iptables -A drop_invalid -j LOG --log-level debug --log-prefix "INVALID state -- DENY "
iptables -A drop_invalid -j DROP

# anti-spoof
iptables -N In_RULE_0
iptables -A INPUT -i enp0s7   -s amarildo   -j In_RULE_0
iptables -A In_RULE_0  -j LOG  --log-level info --log-prefix "RULE 0 -- DENY "
iptables -A In_RULE_0  -j DROP

# ICMP Block - Log
iptables -N In_RULE_1
iptables -A INPUT -p icmp  -m icmp  --icmp-type any  -j In_RULE_1
iptables -A In_RULE_1  -j LOG  --log-level info --log-prefix "RULE 1 -- DENY "
iptables -A In_RULE_1  -j DROP

# Whois - Block - Log
iptables -N In_RULE_2
iptables -A INPUT -p tcp -m tcp  --dport 43  -j In_RULE_2
iptables -A In_RULE_2  -j LOG  --log-level info --log-prefix "RULE 2 -- DENY "
iptables -A In_RULE_2  -j DROP

# xmas-scan - Block - Log
iptables -N In_RULE_3
iptables -A INPUT -p tcp -m tcp   --tcp-flags ALL URG,PSH,FIN  -j In_RULE_3
iptables -A In_RULE_3  -j LOG  --log-level info --log-prefix "RULE 3 -- DENY "
iptables -A In_RULE_3  -j DROP

# xmas-scan-full - Block - Log
iptables -N In_RULE_4
iptables -A INPUT -p tcp -m tcp   --tcp-flags ALL URG,ACK,PSH,RST,SYN,FIN  -j In_RULE_4
iptables -A In_RULE_4  -j LOG  --log-level info --log-prefix "RULE 4 -- DENY "
iptables -A In_RULE_4  -j DROP

# IP fragments - BLock - Log
iptables -N In_RULE_5
iptables -A INPUT -p all  -f   -j In_RULE_5
iptables -A In_RULE_5  -j LOG  --log-level info --log-prefix "RULE 5 -- DENY "
iptables -A In_RULE_5  -j DROP

# who - Block - Log
iptables -N In_RULE_6
iptables -A INPUT -p udp -m udp  --dport 513  -j In_RULE_6
iptables -A In_RULE_6  -j LOG  --log-level info --log-prefix "RULE 6 -- DENY "
iptables -A In_RULE_6  -j DROP

# traceroute - Block - Log
iptables -N In_RULE_7
iptables -A INPUT -p udp -m udp  --dport 33434:33524  -j In_RULE_7
iptables -A In_RULE_7  -j LOG  --log-level info --log-prefix "RULE 7 -- DENY "
iptables -A In_RULE_7  -j DROP

# ESTABLISHED,RELATED
iptables -A INPUT  -m state --state ESTABLISHED,RELATED  -j ACCEPT

# loopback (IN)
iptables -A INPUT -i lo   -m state --state NEW  -j ACCEPT

#(INVALID OUT)
iptables -A OUTPUT -p tcp -m tcp ! --tcp-flags SYN,RST,ACK SYN -m state --state NEW -j DROP

# loopback (OUT)
iptables -A OUTPUT -o lo   -m state --state NEW  -j ACCEPT

# ESTABLISHED,RELATED (OUT)
iptables -A OUTPUT  -m state --state ESTABLISHED,RELATED  -j ACCEPT

# DNS
iptables -A OUTPUT -p tcp -m tcp  --dport 53  -m state --state NEW  -j ACCEPT
iptables -A OUTPUT -p udp -m udp  --dport 53  -m state --state NEW  -j ACCEPT

# FTP
iptables -A OUTPUT -p tcp -m tcp  --dport 21  -m state --state NEW  -j ACCEPT

# http
iptables -A OUTPUT -p tcp -m tcp  --dport 80  -m state --state NEW  -j ACCEPT

# https
iptables -A OUTPUT -p tcp -m tcp  --dport 443  -m state --state NEW  -j ACCEPT

# IMAP
iptables -A OUTPUT -p tcp -m tcp  --dport 143  -m state --state NEW  -j ACCEPT

# POP3
iptables -A OUTPUT -p tcp -m tcp  --dport 110  -m state --state NEW  -j ACCEPT

# Printer
iptables -A OUTPUT -p tcp -m tcp  --dport 515  -m state --state NEW  -j ACCEPT

# SMTP
iptables -A OUTPUT -p tcp -m tcp  --dport 25  -m state --state NEW  -j ACCEPT

# SMTPS
iptables -A OUTPUT -p tcp -m tcp  --dport 465  -m state --state NEW  -j ACCEPT

# OpenVPN
iptables -A OUTPUT -p udp -m udp  --dport 1194  -m state --state NEW  -j ACCEPT

# Kpasswd
iptables -A OUTPUT -p udp -m udp  --dport 464  -m state --state NEW  -j ACCEPT

# ALL UDP
iptables -N RULE_21
iptables -A OUTPUT -p udp -m udp  -j RULE_21
iptables -A INPUT -p udp -m udp  -j RULE_21
iptables -A RULE_21  -j LOG  --log-level info --log-prefix "RULE 21 -- DENY "
iptables -A RULE_21  -j DROP

# ALL TCP
iptables -N RULE_22
iptables -A OUTPUT -p tcp -m tcp  -j RULE_22
iptables -A INPUT -p tcp -m tcp  -j RULE_22
iptables -A RULE_22  -j LOG  --log-level info --log-prefix "RULE 22 -- DENY "
iptables -A RULE_22  -j DROP

# All other attempts are denied and logged
iptables -N RULE_23
iptables -A OUTPUT  -d amarildo   -j RULE_23
iptables -A INPUT  -j RULE_23
iptables -A RULE_23  -j LOG  --log-level info --log-prefix "RULE 23 -- DENY "
iptables -A RULE_23  -j DROP

# Logged again
iptables -N RULE_24
iptables -A OUTPUT  -j RULE_24
iptables -A INPUT  -j RULE_24
iptables -A RULE_24  -j LOG  --log-level info --log-prefix "RULE 24 -- DENY "
iptables -A RULE_24  -j DROP