View IPTables blocks

To view iptables blocks, you can use the following commands:

1. List all active rules: iptables -L (or iptables -nL for numerical output)
   • This command lists all active rules in all chains (INPUT, OUTPUT, FORWARD, etc.).
2. List rules for a specific chain: iptables -L <chain_name>
   • Replace <chain_name> with the name of the chain you’re interested in (e.g., INPUT, OUTPUT, FORWARD).
3. View detailed information: iptables -L -v -n
   • This command provides detailed information about each rule, including packet and byte counters.
4. Search for a specific IP address: iptables -L -n --line | grep <IP_Address>
   • Replace <IP_Address> with the IP address you’re interested in. If the IP appears as DROP or REJECT, it’s blocked.
5. View rules with line numbers: iptables -L -n --line-numbers
   • This command adds line numbers to the output, making it easier to identify specific rules.

Below shows an example of using iptables -L -v -n:

Chain INPUT (policy DROP 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination
 284K   42M ACCEPT     all  --  any    any     anywhere             anywhere             ctstate RELATED,ESTABLISHED
    0     0 ACCEPT     all  --  lo     any     anywhere             anywhere
    0     0 DROP       all  --  any    any     anywhere             anywhere             ctstate INVALID
  396 63275 UDP        udp  --  any    any     anywhere             anywhere             ctstate NEW
17067 1005K TCP        tcp  --  any    any     anywhere             anywhere             tcp flags:FIN,SYN,RST,ACK/SYN ctstate NEW
 2410  154K ICMP       icmp --  any    any     anywhere             anywhere             ctstate NEW
  396 63275 REJECT     udp  --  any    any     anywhere             anywhere             reject-with icmp-port-unreachable
 2916  179K REJECT     all  --  any    any     anywhere             anywhere             reject-with icmp-proto-unreachable
    0     0 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:ssh ctstate NEW,ESTABLISHED