Nothing was recorded in the syslog file, because no action has (yet) been taken by iptables. Here is what was recorded in the local Apache access log: 10.0.1.4 - "GET / HTTP/1.1" 200 54124 "-" "Wget/1.16 (linux-gnueabihf)" A simple fetch of the Apache front page was enough. A wget command will be issued on that system, directed at the system with the new ipset blacklist. Monitoring the Apache access log and the syslog file (where iptables logs to) in the current shell will cause messages of interest to appear immediately: # tail -f /var/log/apache2/access.log & ![]() First though, let’s see what a legitimate web hit looks like. To demonstrate that the iptables list is working, the address of a local test system will be added to the list blacklist1. ![]() To check that the list is working, we can either wait until some traffic happens to come in from those excluded IP addresses, or do a quick test. LOG all - anywhere anywhere match-set blacklist1 src LOG level warning prefix "Blocked by IPset: "ĭROP all - anywhere anywhere match-set blacklist1 src List the firewall rules, and the new entries are shown. The first command just creates a message in the logs, recording the block. Note: the block is performed by the second command. # iptables -A INPUT -m set -match-set blacklist1 src -j DROP # iptables -A INPUT -m set -match-set blacklist1 src -j LOG -log-level 4 -log-prefix "Blocked by IPset: " Here are two commands to make the firewall block all IP addresses in the list. To make use of the new list, iptables needs to be reconfigured. Incorporating an Ipset List into the Firewall We could add many more addresses, but just leave it at these two for now. The attack was over after a few hours, but let’s block them anyway. These two were responsible for an (unsuccessful) dictionary attack on one of our WordPress platforms in March 2016. Add IP AddressesĪdd a couple of IP addresses to the list. “Members” is blank because so far the list is empty. Header: family inet hashsize 1024 maxelem 65536 The ipset list command can be used to view our new list: # ipset list ![]() The “hash:ip” bit tells the ipset command to use a hash table to store items, and that the items will be ip addresses. Let’s call it blacklist1 # ipset create blacklist1 hash:ip An ipset list can contain other items, but this article will focus on IP addresses.Ĭreate a list as follows. The purpose of ipset is to create and manage lists of IP addresses in the kernel, using efficient structures to allow quick lookup. On Debian and its descendants, apt-get install ipset. On Red Hat and related systems, yum install ipset should do it. In short, ipset allows a large number of IP addresses to be blocked in an efficient way, as demonstrated below. This means it is supported in Debian 7 and 8, as well as Red Hat 6 onwards. Ipset is a fairly recent addition to Linux, having been introduced into kernel version 2.6.32. Iptables is most useful, perhaps, on those servers most susceptible to attack, such as LAMP systems, content management servers and blogging platforms like WordPress, especially where they are Internet facing. ![]() Often referred to simply as “ iptables“, it is a basic firewall built into the Linux kernel. The Linux packet filter provides an easy way to protect against unwanted network intrusions.
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