Configuring a good firewall is a basic task when securing modern operating systems. Iptables is the standard included in most Linux distributions, at least until nftables replaces it. In this article, we will learn how to configure iptables rules using a Python script.

We install the necessary Python module using pip:

In this example, we will program a basic script where we block an IP address A.B.C.D and verify that the rule has been inserted:

import iptc

rule = iptc.Rule()
rule.src = "A.B.C.D"
rule.create_target("DROP")
rule.target = iptc.Target(rule, "DROP")
chain = iptc.Chain(iptc.Table(iptc.Table.FILTER), "INPUT")
chain.insert_rule(rule)

rawdata = iptc.easy.dump_table('filter', ipv6=False)

for rule in rawdata['INPUT']:
    print rule
    if 'src' in rule and 'target' in rule:
        if rule['src'] == 'A.B.C.D/32' and rule['target'] == 'DROP':
            print 'Matched rule'