142 lines
7.6 KiB
Markdown
142 lines
7.6 KiB
Markdown
blacklist-scripts
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=================
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This is a collection of shell scripts that are intended to block Linux systems and OpenWRT routers from known sources of malicious traffic. These scripts use `iptables` with highly efficient `ipset` module to check incoming traffic against blacklists populated from publicly available sources.
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[Emerging Threats](http://rules.emergingthreats.net/fwrules/) provides similar rules that essentially run `iptables` for *each* blacklisted IP which is extremely inefficient in case of large blacklists. Using `ipset` means using just one `iptables` rule to perform a very efficient lookup in hash structure created by `ipset`.
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## Available blacklists
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* [Emerging Threats](http://rules.emergingthreats.net/fwrules/) - list of other known threats (botnet C&C, compromised servers etc) compiled from various sources, including [Spamhaus DROP](http://www.spamhaus.org/drop/), [Shadoserver](https://www.shadowserver.org/wiki/) and [DShield Top Attackers](http://www.dshield.org/top10.html)
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* [www.blocklist.de](https://www.blocklist.de/en/index.html) - list of known password bruteforcers supplied by a network of [fail2ban](http://www.fail2ban.org/wiki/index.php/Main_Page) users
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* [iBlocklist](https://www.iblocklist.com/lists.php) - various free and subscription based lists
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* [Bogons](http://www.team-cymru.org/Services/Bogons/) - IP subnets that should never appear on public Internet; this includes [RFC 1918](http://tools.ietf.org/html/rfc1918) networks so running this on a machine in a private network will effectively **shut its networking down**
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By default the script will only load Emerging Threats and Blocklist.de collections. Others may be added by simply appending to the `urls` variable in the beginning of the script:
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urls="http://rules.emergingthreats.net/fwrules/emerging-Block-IPs.txt"
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urls="$urls https://www.blocklist.de/downloads/export-ips_all.txt"
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The script ignores empty lines or comments and will only extract anything that looks like an IP address (`a.b.c.d`) or CIDR subnet (`a.b.c.d/nn`). Each blacklist is loaded into a separate `ipset` collection so that logging unambigously identifies which blacklist blocked a packet.
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The script also created an empty `manual-blacklist` set that can be used by the administrator for manual blacklisting. For example:
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ipset add manual-blacklist 217.146.93.122
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Removal:
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ipset delete manual-blacklist 217.146.93.122
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## OpenWRT
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The script automatically detects OpenWRT environment (looking for `uci`) and will try to obtain the WAN interface name. The filtering will be then **limited to WAN interface only.**
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Requirements:
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* `opkg install ipset curl`
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Installation:
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cp blacklist.sh /etc/firewall.user
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echo "01 01 * * * sh /etc/firewall.user" >>/etc/crontabs/root
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The blacklist will be updated on daily basis.
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Manual run:
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sh /etc/firewall.user
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## Linux
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Requirements:
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* On Debian, Ubuntu and other `apt` systems: `apt-get install ipset curl`
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* On RedHat, Fedora, CentOS and other RPM systems: `yum install ipset curl`
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Installation:
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cp blacklist.sh /etc/cron.daily/blacklist
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The blacklist will be updated on daily basis.
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Manual run:
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sh /etc/cron.daily/blacklist
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# Integration with OSSEC
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[OSSEC HIDS](http://www.ossec.net/) is a host-intrusion detection engine for Unix and Windows servers. Its [active response](http://ossec-docs.readthedocs.org/en/latest/manual/ar/index.html) feature allows running a script in response to configured events, for example blocking an IP address detected as attempting to continuously bruteforce a SSH password.
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The `ipset-drop.sh` is active response script to add offending IP addresses to a `manual-blacklist` set also created by the `blacklist.sh` script.
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Installation:
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cp ipset-drop.sh /var/ossec/active-response/bin
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Example OSSEC configuration:
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<command>
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<name>ipset-drop</name>
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<executable>ipset-drop.sh</executable>
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<expect>srcip</expect>
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<timeout_allowed>yes</timeout_allowed>
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</command>
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<active-response>
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<command>ipset-drop</command>
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<location>local</location>
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<rules_id>5720</rules_id> <!-- Rule: 5720 fired (level 10) -> Multiple SSHD authentication failures. -->
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</active-response>
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Another script `router-drop.sh` will perform the same action on a remote router over SSH. This is useful in case of embedded routers where OSSEC agent installation is unfeasibile. OpenWRT logs (over syslog) to a more powerful Linux box with OSSEC installed. On alerts the active response script installed that blocks uoffending IP addresses on the router:
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```
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+---------+ ----- syslog -------> +-------+
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--| OpenWRT | | Linux |
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| | | OSSEC |
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+---------+ <- active response -- +-------+
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```
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The `router-drop.sh` script requires two configuration steps:
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* configure the `ROUTER` variable to a SSH string for root login to the router (e.g. *root@gw.example.com*)
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* install SSH keys to actually log in; the keys need to be installed on root account as this is where active response script are running
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Example configuration:
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<command>
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<name>router-drop</name>
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<executable>router-drop.sh</executable>
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<expect>srcip</expect>
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<timeout_allowed>no</timeout_allowed>
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</command>
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<active-response>
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<command>router-drop</command>
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<location>local</location>
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<rules_id>51004</rules_id>
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</active-response>
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Event 51004 is defined in `/var/ossec/rules/dropbear_rules.xml` and triggered by a series of unsuccessful password logins. Don't forget to add your trusted networks to `<white_list>` entries to prevent locking yourself out!
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## Samples
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Number of blacklisted IP addresses:
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# ipset list | wc -l
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26160
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Traffic (ICMP and TCP) from blacklisted IP addresses in router logs (OpenWRT):
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# dmesg|grep BLOCK
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[745433.590000] BLOCK emerging-Block-IPs.txt IN=eth0.2 OUT=br-lan MAC=64:70:12:c2:64:70:02:cc:24:73:9c:97:26:50:b9:10:08:00 SRC=217.146.93.122 DST=10.10.10.20 LEN=28 TOS=0x00 PREC=0x00 TTL=56 ID=54090 PROTO=ICMP TYPE=0 CODE=0 ID=48891 SEQ=0 MARK=0x10
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[745433.620000] BLOCK emerging-Block-IPs.txt IN=eth0.2 OUT=br-lan MAC=64:70:12:c2:64:70:02:cc:24:73:9c:97:26:50:b9:10:08:00 SRC=144.76.71.210 DST=10.10.10.20 LEN=28 TOS=0x00 PREC=0x40 TTL=51 ID=17805 PROTO=ICMP TYPE=0 CODE=0 ID=28814 SEQ=0 MARK=0x10
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[745484.510000] BLOCK emerging-Block-IPs.txt IN=eth0.2 OUT=br-lan MAC=64:70:12:c2:64:70:02:cc:24:73:9c:97:26:50:b9:10:08:00 SRC=69.194.235.103 DST=10.10.10.20 LEN=44 TOS=0x00 PREC=0x00 TTL=45 ID=0 DF PROTO=TCP SPT=443 DPT=58827 WINDOW=5840 RES=0x00 ACK SYN URGP=0 MARK=0x33
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Traffic (SSH bruteforce scanners) from blacklisted IP addresses in web server logs (CentOS):
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BLOCK export-ips_all.txt IN=eth1 OUT= MAC=bc:16:2e:08:69:d4:3c:08:f6:d9:93:a5:08:00 SRC=122.225.97.79 DST=10.179.134.230 LEN=40 TOS=0x00 PREC=0x00 TTL=101 ID=256 PROTO=TCP SPT=6000 DPT=22 WINDOW=16384 RES=0x00 SYN URGP=0
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BLOCK export-ips_all.txt IN=eth1 OUT= MAC=bc:16:2e:08:69:d4:3c:08:f6:d9:93:a5:08:00 SRC=61.174.51.207 DST=10.179.134.230 LEN=40 TOS=0x00 PREC=0x00 TTL=102 ID=256 PROTO=TCP SPT=6000 DPT=22 WINDOW=16384 RES=0x00 SYN URGP=0
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Traffic (SSH password bruteforce scanners) blocked by [OSSEC HIDS](http://www.ossec.net/) (Linux):
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BLOCK manual-blacklist IN=eth1 OUT= MAC=bc:76:2e:08:69:d4:3c:08:f6:d9:93:a5:08:00 SRC=89.46.14.48 DST=10.179.134.230 LEN=60 TOS=0x00 PREC=0x00 TTL=48 ID=62214 DF PROTO=TCP SPT=51436 DPT=22 WINDOW=5840 RES=0x00 SYN URGP=0
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BLOCK manual-blacklist IN=eth1 OUT= MAC=bc:76:2e:08:69:d4:3c:08:f6:d9:93:a5:08:00 SRC=89.46.14.48 DST=10.179.134.230 LEN=60 TOS=0x00 PREC=0x00 TTL=48 ID=62215 DF PROTO=TCP SPT=51436 DPT=22 WINDOW=5840 RES=0x00 SYN URGP=0
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