Taming the beasts… aka suricata blueprint
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@jflsakfja:
In order to determine what rules to enable for lan facing and wan facing interfaces, you need to go through the rules one by one, looking at their sources and destinations. I'm having a hard time keeping up as it is, imagine that as well :p
The easy way out is to enable 2 identical interfaces, one on wan and one on lan. We've already trimmed down suricata enough for that to run OK, assuming you have at least a decent amount of RAM (4GB).
Whether an internal facing interface is really needed, it's another question. Most "malware" rules have rules for both directions (in + out) so the wan one should spot something fishy easily. If you have multiple lan interfaces, that add yet another question. How will pfsense analyze traffic from LAN1 to LAN2? It needs an internal facing interface.
Questions, questions. Answer 1 and 1000 will pop up :p
Thank you ;D
Well, if the rulesets are available somewhere for import in MS Excel, and if I would really understand what I need to look for (the part in bold in your reply, which I don't quite understand yet, as in: what do I need to look for exactly?), I could try to filter out in Excel the rules that need to go on WAN, versus the ones that need to go on LAN.
I'm more than willing to attempt an effort at that, but you would need to give this noob slightly more detailed instructions on what to look for :P
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Text copied from edit rules tab, so the columns are:
SID PROTOCOL SOURCE DESTINATION EXPLANATIONWAN facing rule:
2017397 http $EXTERNAL_NET any $HOME_NET any ET DOS Apple CoreText Exploit Specific string
Notice the red text in the source. It means a source that is not us(= every other on the Internet => WAN facing)LAN facing rule:
2017920 udp $HOME_NET 123 $EXTERNAL_NET any ET DOS Possible NTP DDoS Multiple MON_LIST Seq 0 Response Spanning Multiple Packets IMPL 0x02
Notice the blue text in the source. It means a source that is us (=> internally facing)BOTH facing rule: (WAN+LAN, must be duplicate)
2017919 udp any any any 123 ET DOS Possible NTP DDoS Inbound Frequent Un-Authed MON_LIST Requests IMPL 0x03
Notice the green text in the source. It means a source that is any(ie we are not sure if it's us or them) => it needs to be duplicated to both internally and externally facing interface/s. -
That's great, BB ;D
The noob at it again: to which categories do you need to add these in the script? Simply copy line X in the script and change the URL?
You can add a new line below the Abuse Palevo list as follows:
collect "$sch4" "AbuseSSLBL|tier1|https://sslbl.abuse.ch/blacklist/|sslipblacklist.csv|process|yes|yes|faf"
I am showing the conservative list in this example, you can also use the aggressive one if you choose. I am away until early next week so I can't provide any advice until I test it my self. There are not that many IPs in the aggressive file, so even if there are FPs, probably wouldn't be many to deal with.
In regards to disabling those rules. The ones I posted above, you can disable the whole category in the category tab for the WAN interface, you don't need to do this one rule at a time.
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@Hollander, you have to jump in and learn some Linux CLI like the "grep" command. Google it and you will see how powerful this command is.
The rules files are located in these folders depending on your OS type and Snort/Suricata:
Snort64. /usr/pbi/snort-amd64/etc/snort/rules
Snort32. /usr/pbi/snort-i386/etc/snort/rules
Suri64. /usr/pbi/suricata-amd64/etc/suricata/rules
Suri32. /usr/pbi/suricata-i386/etc/suricata/rules
So as an example:
grep "$EXTERNAL_NET" /usr/pbi/suricata-amd64/etc/suricata/rules/*
Note to add a "" to escape special characters, as $ is used as a variable name.
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If non-transparent proxy is being used, there is no real point in running Snort or Suricata with blocking enabled on LAN interface - all connections will be between internal hosts and LAN interface IP where proxy is listening. By default, those are whitelisted and if you decide to block internal hosts, you will cut off them from the internet completely…
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If non-transparent proxy is being used, there is no real point in running Snort or Suricata with blocking enabled on LAN interface - all connections will be between internal hosts and LAN interface IP where proxy is listening. By default, those are whitelisted and if you decide to block internal hosts, you will cut off them from the internet completely…
I'm not understanding this. Are you saying that they be able to alert correctly since they are going thru a proxy? I run a non-transparent proxy, using wpad.. Snort and Suricata have been alerting correctly and block external IPs when needed. During testing, ET Policy were the block of my alerts on the LAN interface..
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When internal client goes through non-transparent proxy, Suricata will only see internal IPs on LAN interface.
If there is some alert - let's say malicious JavaScript - it will alert, but since all IPs are local (ex. 192.168.1.1:55555 -> 192.168.1.1:8080), it won't block anything. For this to block, you have to catch this connection on WAN interface. -
If non-transparent proxy is being used, there is no real point in running Snort or Suricata with blocking enabled on LAN interface - all connections will be between internal hosts and LAN interface IP where proxy is listening. By default, those are whitelisted and if you decide to block internal hosts, you will cut off them from the internet completely…
Are you talking about a transparent firewall running snort/suricata? There are uses for this, no it's not for everyone. By default snort/suricata has difficulty determining its IPs when running in transparent mode, so no hosts will be whitelisted. Ask yourself. What would you pick? System compromise or system getting cut off from the internet? If an internal server is infected somehow and starts spewing exploits here and there, the acceptable way of dealing with it is cutting off its network access. Care! There have been cases (supposedly) in the past where malware was (allegedly) designed to that if you pulled the ethernet cable it would start destroying the system's filesystem.
A transparent snort/suricata system comes in handy when you don't want hosts on the network being able to access it in any way. How will you attack the upstream gateway if you don't know there IS an upstream gateway?
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Hmm… I thought, I clearly wrote:
If non-transparent proxy is being used…
Let me try one more time - if you do NOT run proxy (Squid or anything else) in transparent mode - which means internal machine browser have to specify proxy in the browser, which, in turn, means that internal machine will connect to proxy in order to request any web page - in this case, running Snort/Suricata riles, which check any protocols, which proxy can rely (ex. HTTP, HTTPS, FTP) is possible in alert mode only. Even if you check to block, by default connections will not be blocked, because they are only between internal machine and LAN interface IP and those IPs are whitelisted by Snort/Suricata as internal network.
See example in the attached screenshot. In there, 192.168.15.56 is the internal IP of the pfSense, which has Snort listening on port 8080 and 192.168.15.174 is the client, receiving obfuscated JavaScript in the web response. Snort will not block this because all IPs are internal.
In this case, if such blocking is required, appropriate rules should be activated on WAN interface, but you will not see internal IP in the alerts.
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Transparent or not the proxy will still not be blocked, since it's a known IP by snort/suricata. (WAN interface).
It will block the external host though, as long as it can see inside the protocol (ie no TLS).
If you want to block internal hosts, then just change the pass list to a different one. Snort/suricata will think all systems are to be blocked (even internal IP ones) if you have it listening on an internal interface.
EDIT:brain fart :p
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Transparent or not the proxy will still not be blocked, since it's a known IP by snort/suricata. (WAN interface).
Sorry, not sure I understand you - do you have your proxy listening on WAN interface?
If you want to block internal hosts, then just change the pass list to a different one. Snort/suricata will think all systems are to be blocked (even internal IP ones) if you have it listening on an internal interface.
What is "it" in here? Proxy?
Entire internal network is in the pass list by default.
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Snort/suricata WAN interface. No matter what proxy you run internally, eventually it must connect to the outside to pull data in. That's when the alerts will fire up. Snort/suricata will try to ban both source+destination (if you did not set it up like that, you should) and since the destination (proxy) is listed on its (snort/suricata's) pass list, it (proxy) will not be blocked. The outside IP will though.
WRT the listening, I was talking about snort/suricata.
"Entire internal network is in the pass list by default." I am aware of that, that's why I said change the pass list. If you tell suricata these are the networks you should NOT ban, but do NOT include the private IPs in that list, suricata will notice the alert, check to see if a private IP is on the pass list, NOT see the IP there, therefore will proceed to ban the internal IP. Most likely the proxy (pfsense) will be banned as well, so that IP should be on the pass list.
If I still fail to see the point, my apologies, it was a long day.
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Yeah, I think we speak different languages.
I am not talking about WAN interface, not sure why you brought it in.
I am talking about Snort/Suricata instance on LAN interface. In case of non-transparent proxy it does not see external IPs, period.
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WAN is brought in because it is needed to connected to the outside world. If you have the same rules on both interfaces and an alert pops up; the WAN interface will block the the external IP. interface. Since you should have the same alert for both interfaces, you can cross reference the WAN/LAN alert logs to find the internal IP on your LAN interface. I get what you're saying now about the LAN not blocking the the internal IP since its already white-listed. I haven't had any LAN clients stumble any malicious javascript yet.
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Yeah, I think we speak different languages.
I am not talking about WAN interface, not sure why you brought it in.
I am talking about Snort/Suricata instance on LAN interface. In case of non-transparent proxy it does not see external IPs, period.
snort/suricata interface on LAN should show the same alert that snort/suricata on the WAN will show. If you did change the pass list, then both the internal (private) IP and the external (malicious site) IP will be blocked. If you still think that pfsense will not see the internal IP because it somehow "travels through the proxy" then you are missing a critical piece of information. snort/suricata are running the interfaces as promiscuous. That means they see every single packet that hits them, even if it's not destined for them. snort/suricata will see the packets from the laptop to the proxy (assuming proxy on pfsense), the proxy's answer to the laptop (both on LAN interface) and the request from the proxy to the malicious site, and the malicious site answer to the proxy (WAN interface). Anything that flags an alert with any of that will result in an IP being blocked, even internal IPs. Period. (throwing it in there, since something clicks in my head when someone says period to me, then everything turns black).
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If you have the same rules on both interfaces and an alert pops up; the WAN interface will block the the external IP. interface. Since you should have the same alert for both interfaces, you can cross reference the WAN/LAN alert logs to find the internal IP on your LAN interface. I get what you're saying now about the LAN not blocking the the internal IP since its already white-listed. I haven't had any LAN clients stumble any malicious javascript yet.
Yes, that is the point I am trying to make - in such case you have to have appropriate rules enabled on WAN interface and, as you said, there is a need to find which internal IP it was, on the LAN interface as well… But that is a lot of manual labor to cross-reference alert logs :( And the additional memory used for duplicate rules...
For me, Snort http preprocessor with its built-in inspection rules (like (http_inspect) HTTP RESPONSE HAS UTF CHARSET WHICH FAILED TO NORMALIZE) is too noisy and blocks normal sites often.
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@jflsakfja:
Anything that flags an alert with any of that will result in an IP being blocked, even internal IPs.
Don't know about you, but in my setup internal IPs are in the safe list by default (did I repeat it 3rd time?).
Oh, and I am not complaining about that. -
@jflsakfja:
Anything that flags an alert with any of that will result in an IP being blocked, even internal IPs.
Don't know about you, but in my setup internal IPs are in the safe list by default (did I repeat it 3rd time?).
Oh, and I am not complaining about that.I also repeated 3 times that you can actually change the PASS list so they are not.
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And why would I need to remove my internal network from the pass list?
What is the use case? May be for some public hotspot it may make sense, but not for the trusted network… -
There is no such thing as a trusted network. As I said somewhere else, the only thing you should trust is the little voice inside your head. Everything/everyone out there is out to get you. And no, it's not paranoia when they ARE out to get you.
NSA aside, the use case is when trying to limit a local (internal) host from spreading something nasty on the internet. Other than that, there is no use for it, since it can still spread the "nasty" to other hosts on its subnet. When each host is on a different subnet, that's a different story, it effectively blocks it from accessing the entire network, but that is a highly specialized use case (ie not something you will encounter outside of an ISP).
Another use case that pops into my mind is when providing internet access to others (free wifi anyone?). You can't tell what their systems are infected with, so to limit your liability you could block it from accessing the internet.
As you can see from the guide, most weight is put into securing the network from outside threats, with some weight given on somewhat limiting outgoing connections. My recommendation for a normal home network is to use your trusted network example. Perfectly normal paranoia aside, it's very unlikely the NSA has broken into your house/computer-while-it-was-shipped and installed a backdoor. Incoming "nasties" are blocked. Since they are blocked, and you use some common sense (a shocking truth, but that hottie that keeps sending you naked images of her, is actually trying to get your email client to parse a command obfuscated in the image, ala firefox (yes a browser) jpg code execution), your network is (mostly) safe. Yes there are other attack vectors (eg browser memory mismanagement) but those are outside the scope of this guide :D.
