Taming the beasts… aka suricata blueprint
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Writing custom rules for deep packet inspection
Suricata's intended use is intercepting the packets as they are passing through the network, reassemble them (if needed), open them up and peek inside, looking for specific patterns, and deciding whether to alert or not (or drop, if running in IPS).We'll examine a specific example of a known spammer trying to send spam to our email server.
The logs show this:
2014-06-24T16:35:52+03:00 emailserver1 postfix/smtpd[4324]: NOQUEUE: reject: RCPT from unknown[192.168.1.1]: 554 5.7.1 Service unavailable; Client host [192.168.1.1] blocked using zen.spamhaus.org; http://www.spamhaus.org/query/bl?ip=192.168.1.1; from= example@example.comto= example2@example2.comproto=ESMTP helo=<[192.168.1.1]>The red part shows that the email was rejected because we have set up our email server so that it first checks if the sender is a known spammer, then decides whether to accept the email or not.
The blue part is the server's reply sent to the client (the spammer).Why not use the IP directly in an alias on pfsense? This is not the scope of this post. This post tries to show how to write custom rules based on what you are trying to detect.
Back on topic. We know so far that we are looking for a packet that is originating from our email server (port 25 since that is unencrypted), and could end up anywhere on the internet, containing a specific reply.
So far the rule is:
alert tcp $SMTP_SERVERS 25 -> $EXTERNAL_NET any
This will not get you far, since you detected ALL traffic originating from port 25, with no specific contents.Examining our reply sent back to the client we see that the easiest way to detect this specific traffic is to use the part in red shown below. This is the common part for all replies, and states the reason why the email was denied:
554 5.7.1 Service unavailable; Client host [192.168.1.1] blocked using zen.spamhaus.org; http://www.spamhaus.org/query/bl?ip=192.168.1.1Ok, now we know what we are looking for, but it's time for us to understand our alert.
Our chosen message will be:
Known SPAMMER
The classification for this alert will be bad-unknown (use http://manual.snort.org/node31.html#SECTION00446000000000000000 and choose the most appropriate classtype for your rule)
Our rule version (revision) will be 1
Our sid (signature ID) must be a high value so that it will not interfere with other rules. Each rule MUST have a unique ID! I recommend using a value in the 9mil range. In this rule we use 9900003 because we have other custom rules before it.Don't forget that we are only interested in established connections (actively communicating) and the traffic direction is from the server to the client.
Putting it all together gives us this:
alert tcp $SMTP_SERVERS 25 -> $EXTERNAL_NET any (msg:"Known SPAMMER"; flow:established,from_server; content:"blocked using"; classtype:bad-unknown; sid:9900003; rev:1;)An example of the alert generated:
2014-06-24T16:09:49+03:00 pfsense1 suricata[21435]: [1:9900003:1] Known SPAMMER [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.200.1:25 -> 192.168.1.1:63651Since our IP is not banned, suricata will try to ban both IPs (source+destination) (ALWAYS set it up like that) but ignore the source.
We have caught our first offender using suricata's deep packet inspection! :D
The spammer will return after 28 days (since his IP will be unbanned) and try to send another spam email. He will be blocked again for a further 28 days. 1 email per month is nothing compared to 1000 per day.
Taking apart the rule and finding flaws (if any)
The rule should only fire up on messages originating from our email servers. Good!
The rule cannot generate a false positive since the email WILL be rejected regardless by our email server. Good!
The rule shows a generic alert message. Good AND Bad!
The rule's alert message is good in the sense that it does not give too much information about the origin of the block (no list's name appears).This is the bad part. This also allows us to keep the alerts tab clean, since a known spammer is a known spammer regardless of where the intel is coming from. If an IP is listed on list ABC on one month, and list DEF on the next month, two alerts will be logged in the alerts tab. For now it's nothing. Detecting a portscan using my previously recommended rule would end up with a thousand alerts logged on the alerts tab for that IP (NOT if using a generic "Incoming connection to unused port" message). This is the good part!Congratulations. You have now finished your training and are part of the industry's elite in network security. You are one of the best in this field! Use the knowledge wisely./example2@example2.com/example@example.com
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great work jflsakfja!
You may want to add decoder-events - 2200013 IPv6 truncated packet to the list for noise. My alert file is mostly this alert. What is strange, none of these show up in the GUI, only in the Alert file itself… Because there is no IP, i'm thinking the GUI doesn't display it. But that's for another thread after I confirm my findings.
06/25/2014-06:27:46.251740 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.250371 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.318718 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.251489 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.319106 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.319352 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.543947 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 0A B8 B0 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.319496 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.543837 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 0A B8 B0 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.986163 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 05 E7 64 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.986289 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 05 E7 64 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] -
Getting the suricata logs on a remote syslog, and I'm running IPv6 tunnels because my upstream provider has vowed not to support IPv6 until AFTER they are completely cut off from the Internet (it will be the last ISP on earth that moves to IPv6). It might be due to the fact that their "3rd level" support technicians have no clue what an IP (4 or 6) address looks like. This is the same company that has to pay a daily fine for "excessive profits".
I've not seen that alert so far, but I'll keep an eye out for it, thanks for pointing it out.
So far the list seems to have stabilized a LOT, and I'm thinking about clearing up the list (# and no # rules). What gets on my nerves is that although the list originates from the snort topic (which is almost a year old!) most of the rules are still there.
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I'm wondering since i'm dual stack IPv4/IPv6(DHCP for both on the WAN), that is why i'm seeing this alert.. My ISP(TWC) doesn't officially support IPv6 but its enabled and working pretty well. Better then IPv4 traffic at times…
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I also dual stack, but have not seen that alert yet. Same here, I get better speeds over the tunnel, than the native IPv4.
On a side note, I'm updating the list. Mostly cleaning it up, moving the DO NOT USE! categories to the top so it's easier to find them, removing the # and no # rules…a line added here, a line taken away there...deleting some rules, updating the counts. I said I'm rarely mistaken (mathematically proven by the world's top universities, and the possibility of me being mistaken comes out to 0.000000000001%) but ffs guys. 5 rules on top of a count that says 4 rules are disabled should be noticed by someone by now :D.
EDIT: Finished cleaning up. The list is now starting fresh for suricata (old rules coming over from snort that did not FP within a reasonable timeframe were removed), cleaned up and ready to go. Enjoy!
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whitelists were renamed to passlists not long ago. That is a definite bug in the suricata package. please post a link pointing to that post, on the most recent version(ed?) topic on suricata or re-post the same thing there. I'm not the suricata package maintainer, bmeeks is ;D
bmeeks got a tunnel working a few days back, so IPv6 support for both packages should improve.
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@jflsakfja:
I also dual stack, but have not seen that alert yet. Same here, I get better speeds over the tunnel, than the native IPv4.
On a side note, I'm updating the list. Mostly cleaning it up, moving the DO NOT USE! categories to the top so it's easier to find them, removing the # and no # rules…a line added here, a line taken away there...deleting some rules, updating the counts. I said I'm rarely mistaken (mathematically proven by the world's top universities, and the possibility of me being mistaken comes out to 0.000000000001%) but ffs guys. 5 rules on top of a count that says 4 rules are disabled should be noticed by someone by now :D.
EDIT: Finished cleaning up. The list is now starting fresh for suricata (old rules coming over from snort that did not FP within a reasonable timeframe were removed), cleaned up and ready to go. Enjoy!
You're dual stack and using a Tunnel? When I mean dual stack; I mean receiving IPv4 IPv6 addresses on the same WAN interface.. The alerts are on that interface… Once I get my stuff fine tune, i'm going to copy it over to LAN and see if there is a difference. I should had started with my LAN interface first but oh well...
I noticed the counts were wrong, figured your eyes were getting crossed or something from the long post :o Thanks again for a great thread!
@avink use this topic https://forum.pfsense.org/index.php?topic=73906.msg428032#msg428032 to report the issue
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Statistics on suricata's system usage
While idling, the system is using about 2% CPU and 23% RAM (4GB,32bit so not all available).
Under normal load (not extreme "ZOMG! multiple 10Gbps duplex laser links into space!") the CPU occasionally spikes to <10% for a brief moment, and the RAM stays about the same.
While reloading rules (when hitting save on the rules page or disabling a rule from the alerts tab) the CPU spikes to 50% with it occasionally going higher (seen up to 92% for a few seconds). CPU is a dual core, so 50% means 100% of one core. RAM usage drops at the start of the reload, and continues to slowly climb to ~23% while the rules are reloaded into RAM.
System has been set up according to this topic, with about 50 custom rules. It's the network gateway to a small datacenter, which also provides Internet connectivity for hosts outside the datacenter.
Matcher is AC, suricata interface is WAN.
@Cino : Having a tunnel means somehow getting the IPv6 addresses onto pfsense. Unless you are doing some pretty complicated stuff (routing packets to Mars, then Venus, then the end of the galaxy :D) all other interfaces that need to use those addresses (except the tunnel's "terminating" WAN interface) ARE dual stacked ;). Clients on the LAN side can connect either using an IPv4 address or completely stop using IPv4 and use an IPv6 address. That is the definition of dual stacked :D
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@Cino, Thanks. I removed my message from this thread.
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@jflsakfja:
@Cino : Having a tunnel means somehow getting the IPv6 addresses onto pfsense. Unless you are doing some pretty complicated stuff (routing packets to Mars, then Venus, then the end of the galaxy :D) all other interfaces that need to use those addresses (except the tunnel's "terminating" WAN interface) ARE dual stacked ;). Clients on the LAN side can connect either using an IPv4 address or completely stop using IPv4 and use an IPv6 address. That is the definition of dual stacked :D
Maybe I don't understand but then again I think I do ;) My WAN has both an IPv4 and a IPv6 address, and so does my LAN/Clients.. Before my ISP provided native IPv6; the WAN was IPv4 and I had a separate WAN(Tunneled) Interface for IPv6. That being said, my current WAN/LAN/Clients are all dual stacked. When I only had IPv6 via a tunnel, the LAN and Clients were dual stacked while my WANs were not. Does that make sense?
Question: With a IPv6 Tunnel setup, do you run suricata on that interface also? Or just the IPv4 WAN Interface?
Edit: Noticed emerging-rbn-malvertisers.rules emerging-rbn.rules were not in the DO NOT USE list
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They were supposed to remove those categories since they are no longer maintained. I'll add them in the do not use.
Yes that's what I meant with dual stack.
No need to run suricata on the IPv6 tunnel. It still alerts as is.
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@jflsakfja:
They were supposed to remove those categories since they are no longer maintained. I'll add them in the do not use.
Do you think they will? after reading the comments in your enable rule list; hell will have to freeze over…
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Supposed is the key word :D
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Thank you for taking the time to write up and
giving us this great suricata blueprint,maybe you can help me with this setup
I would like to put pfsense in front of an
existing firewall, but just as an
Suricata IDS and also use the IP Reputation Manager script
is this possible, if it is how would i go about doing
so. The system that i am using has 3 ports, 1 port will be for managing
pfs as a Suricata IDS and the other 2 ports 1 will be connected to the wan of the other firewall
and the other port would be connect to the isp modem.I would like the modem to not see the pfsense Suricata IDS box to act like its not even their and still pass the external address to the
other firewall behind the pfsense Suricata IDS while the pfsense Suricata IDS is still catching the nasty stuff and blocking them. -
great work jflsakfja!
You may want to add decoder-events - 2200013 IPv6 truncated packet to the list for noise. My alert file is mostly this alert. What is strange, none of these show up in the GUI, only in the Alert file itself… Because there is no IP, i'm thinking the GUI doesn't display it. But that's for another thread after I confirm my findings.
06/25/2014-06:27:46.251740 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.250371 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.318718 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.251489 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.319106 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.319352 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.543947 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 0A B8 B0 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.319496 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 01 EA 40 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.543837 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 0A B8 B0 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.986163 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 05 E7 64 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ] 06/25/2014-06:27:46.986289 [**] [1:2200013:1] SURICATA IPv6 truncated packet [**] [Classification: (null)] [Priority: 3] [**] [Raw pkt: 00 25 90 02 31 65 00 01 5C 33 54 41 86 DD 60 05 E7 64 05 B4 06 34 26 10 01 60 00 11 00 11 00 00 ]The GUI is not currently showing these alerts because it is not properly detecting them. The Suricata alert log output is modified to produce a CSV (comma separated values) format. There is a built-in PHP function that can parse a CSV file and split the result into fields. For now the pfSense PHP code is counting fields and only showing on the ALERTS tab those alerts that parse into 13 (I think it is 13) fields. The decoder events currently don't output 13 distinct fields, and hence are dropped by the ALERTS tab PHP code.
I can fix that in an upcoming update.
Bill
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@jflsakfja:
whitelists were renamed to passlists not long ago. That is a definite bug in the suricata package. please post a link pointing to that post, on the most recent version(ed?) topic on suricata or re-post the same thing there. I'm not the suricata package maintainer, bmeeks is ;D
bmeeks got a tunnel working a few days back, so IPv6 support for both packages should improve.
I do finally have a working IPv6 tunnel, and I did see the bug report in a separate post and responded. I will fix it.
Bill
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Thank you for taking the time to write up and
giving us this great suricata blueprint,maybe you can help me with this setup
I would like to put pfsense in front of an
existing firewall, but just as an
Suricata IDS and also use the IP Reputation Manager script
is this possible, if it is how would i go about doing
so. The system that i am using has 3 ports, 1 port will be for managing
pfs as a Suricata IDS and the other 2 ports 1 will be connected to the wan of the other firewall
and the other port would be connect to the isp modem.I would like the modem to not see the pfsense Suricata IDS box to act like its not even their and still pass the external address to the
other firewall behind the pfsense Suricata IDS while the pfsense Suricata IDS is still catching the nasty stuff and blocking them.What you are looking for is running pfsense (+suricata) as a transparent bridge in front of the "normal" firewall. Suricata might have trouble deciding its home net values if running as a bridge (snort did) but that's easily corrected by manually entering the home net.
A transparent bridge is not visible on the network. If you send a packet to one interface, and the rules allow it, it will pop up through the other interface. You can actually do some pretty clever stuff with it, provided you are using a single host (no CARP). Think of it as merging the two interfaces into a single interface, with filtering applied.
A couple of years back I was able to access a public server hosted behind a transparent bridge, from a host on a NATed interface on that transparent bridge (let's say the admin interface), using the server's public IP (universally understood as NOT possible to do). Then again I'm the only person on the planet that managed to get IPv6 working through 30 year old switches :)
That said, my personal recommendation is NOT to run pfsense like that. If you are trying to protect a small network, put pfsense directly as the core router (which allows you to move onto CARP if you so wish), which also saves time (money) + space (1 pc instead of 2 daisy chained firewalls) + power. Then set up firewalls on network hosts, along with other security measures (brute force protection for example) working together to protect your hosts.
EDIT: Clarification: I'm not saying don't ever use transparent bridges. If all you need is a single firewall host, it's actually better to run it as a transparent bridge since the host is not visible from the network. Depending on law mandated paranoia (called certifications in the industry), that might actually be exactly what you should use.
There are also downsides, an example is that the firewall hosts themselves don't have internet access (cannot check for updates), as set up in a plain vanilla transparent bridge (permission is hereby granted to correct me if I'm wrong). -
Awesome post, thanks!
I'm trying to install pfiprep, and am getting an error when installing one of the dependencies.
$ pkg_add -r grepcidr tar: Failed to set default localeCan someone please tell me what to do to fix this?
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$ pkg_add -r grepcidr tar: Failed to set default localeFirst, I would recommend that you make a Full Backup Diagnostics:Backup/Restore (Backup Area "all") and Download configuration… :)
I haven't come across this error on any of my installs or with the ones that I have helped to get working.
What version of pfSense are you using? Is it a Full Install or a Nano version?
Are you seeing any other errors? Could you post the full output of that command?
Can you download the file manually? Maybe a Firewall Rule or Snort is blocking it?
Try to [ [b]ping ftp.freebsd.org ] and see if you get a reply?
[ [b]fetch ftp://ftp.freebsd.org/pub/FreeBSD/ports/amd64/packages-8.3-release/Latest/grepcidr.tbz ]
(This path is for the amd64 Release)[ [b]pkg_add grepcidr.tbz ]
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My cron job is throwing errors.
Since manually running "/usr/bin/nice -n20 /home/badips/pfiprep >> /home/badips/download.log 2>&1" gives me an error "Ambiguous output redirect." .
Leaving out the log output redirect it works fine. (aka >> … or > ...) So I could just remove the log output, but I'd rather keep it. :)For the rest, perfect.
I edited the main script to leave out some lists, and also moved to using the main IR_ lists.
Also great work on the widget.
