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Using Snort Stealthily
jukal writes "Linux Journal has an article on using Snort as stealth sniffer, a stealth NDIS probe and stealth loger -- on a network interface with no IP address. 'Snort is a versatile and powerful tool for sniffing, intrusion detection and packet logging. Configuring it to run stealthily in sniffing mode or NIDS mode is easy; incorporating it into a stealth-logging solution is only slightly less so'"
Snort is a great tool. However, the last time I used it I found it a little bit difficult to get it working just the way I want with all the parameters. In reality, I guess that is probably a good thing or every l33t hax0r would be out there using it.
:)
Regardless- has anyone made any good UI to use it? I really liked the way "sniffit" worked with interactive mode. Maybe someone could design a UI and call it "sniffles" or whatever. The stealth mode version could be called "silent sneeze"
Get real...firewalls are not the "end all" solution to every security problem. You're also mixing passive and active defense. Firewalls are designed to BLOCK attacks at the gateway. Snort (and all network-based IDS') are designed detect attacks that have gotten through your firewall...and they do get through, I assure you.
"Herbivores eat well cause their food never, ever runs."
Unfortunately, firewalls are not the be-all and end-all of network security... A firewall can effectively protect your network from malicious access from the outside world, however it can not prevent hack-attacks on your systems which originate from within your network.
There are two primary reasons for hack-attacks originating inside a firewalled-zone:
1. A trojaned system, usually due to poor Antivirus policy and/or poor user education.
2. A Disgruntled employee who is out to get you!
Obviously, the best solutions to these problems are to implement a good Antivirus product and virus protection policy, and to keep your employees happy!
Unfortunately, no matter how hard you try, there are always likely to be problems you have not forseen - which is where Sniffers and NIDS tools come in. Whilst these tools are also not the sole answer to anyone's prayers, they can often help as part of an overall security system implementation.
Snort is (IMHO) one of the best NIDS tools out there - I have used Snort for a couple of years as part of an integrated security solution, and the logfiles it generates, once properly parsed, have helped me track down a number of threats to network security, and plug any holes present before the problems became serious.
Firewalls are not a panacea, nor are NIDS tools, used together though, they are much more than the sum of their parts....
Disclaimer: I meant what I thought, not what I wrote! What? You can't read my Mind? Oh dear!
Funny, I can have my SNORT installation log to Oracle, MSSQL Server, MySQL, PostGreSQL, etc. And I can perform vulnerability assessments, etc. By adding on ACID (from CERT) and logsnorter, I can integrate my firewall logs and view everything through a very nice web UI. Best of all, except for the hardware I run it on, and the work, my IDS and vulnerability assessment platform hasn't cost me a dime.
And your "superior SQL Server 2000" has more holes than swiss cheese, which is why I'm using MySQL in a secured, private network, for my logs.
In my universe I'm perfectly normal, it's not my fault you don't live in my universe.
The best analogy for defending your networks is a castle. Castles have moats, walls and an inner keep, all to protect the treasures of the kingdom (jewels, the princess, etc.). But, none of that does you any good without sentries watching the moat and walls who can report to the Captain of the Watch anything out of the norm. Your network defense should consist of a hardened router(the moat), firewall and DMZ (walls), and your private networks (the keep). You should have intrusion detection systems, syslogs from routers and firewalls and regular system monitoring (sentries). All of this should be parsed by a system that provides alerts for key events (report to the Captain of the Watch) and is also checked regularly by humans.
In my universe I'm perfectly normal, it's not my fault you don't live in my universe.
You probably should work in the security world before making statements about things you clearly don't understand. tcpdump is a tool for watching all or select traffic. It dumps raw packets, and you have to figure out what to make of them. Snort is a tool for analyzing those packets and alerting on suspicious data. It provides the information you need to help you find potentially dangerous traffic.
Where I work, we have a T-3 'net connection. We typically run about 40% available bandwidth. You'll have just a *TINY* bit of trouble keeping up with that traffic if you manually analyze tcpdump logs. If you run Snort, it will do the bulk of the work, and alert you on things it thinks bear further investigation. It makes mistakes. But having it help focus your traffic checks makes the day a lot easier.
As for using a firewall, too many people have the mistaken impression that once they install a firewall, all their worries will go away. If you have an insider attacking one of your corporate servers, a firewall doesn't help with that at all. An intrusion detection system like Snort will. If you users bring in discs from home that contain trojan programs with call home features, your firewall probably won't catch that, but an intrusion detection system probably will. If your users are surfing to pr0n sites, your firewall might catch that, but an intrusion detection system has a much greater chance.
A firewall is a good thing to have, but everyone working in the security field is going to tell you that it is not enough. We have a concept which we frequently preach to newbs - defense in depth. Put as many systems in place for securing your network as you can realistically manage and track. If you have only a single security device, once an exploit comes out for that device, your network is wide open. And every single security system out there has bugs, so depending on one greatly increases your chances of getting 0wnzerized. Put in multiple systems, and you are likely to catch attacks on at least one of them, in the event that a way to avoid one part of your defense is found.
RagManX
Um, you don't. That's what Gigabit Ethernet is for. Check out the Intel Copper Gig cards - there's Linux support for them and they're reliable cards.
On another note, I don't quite see how using 2 nics, one on a management LAN and the second with no IP bound to it doing the sniffing is a revelation! Shouldn't this just be common sense? After all, it's been a standard NIDS sensor practice for quite a long time now. To really do this job right, all of the sensors should be using a management LAN for reporting back to a MySQL/PostgreSQL database, which in turn is queried by ACID, or something similar..
BTW, ACID's SQL is so terribly un-optimized, it's downright pitiful. I know of a large company that's getting ready to release a huge patch to ACID to actually optimize its SQL usage, bringing performance for large-scale snort deployments up to a reasonable level.
The unsig!
Score: -17, bad security.
Installing a firewall is not a magic solution. Suppose you run a website. You WILL be permitting 80/tcp through your firewall, probably also 443/tcp. Along comes the next worm that uses only http to gain entry to a system (Think CodeRed, Nimda && friends). How exactly is your firewall going to stop that sort of traffic? The answer you're searching for is, "it won't."
In addition to firewalling, running a NIDS sensor will help abate these threats. Most NIDS products support the notion of killing a connection (rskill, for RealSecure, flexresp for Snort, etc.) - this is how you can stop the threat of CR, CR-II, Nimda, et al.
Another way to abate these kinds of threats is to use something like Hogwash (which strangely enough is based on Snort), or a reverse-proxy that can inspect HTTP requests. Of course, those only help for HTTP traffic - there's a lot more out there besides HTTP. Remember sendmail, uw-imap, old qpopper, bind, and friends? They've all had remote-rootables that blew right through firewalls, since they only used the designated "proper" port(s) for the vulnerable daemon.
Use your head. There is no security magic bullet. It's a process, not a single product.
The unsig!
Suppose you run a website. You WILL be permitting 80/tcp through your firewall, probably also 443/tcp. Along comes the next worm that uses only http to gain entry to a system (Think CodeRed, Nimda && friends). How exactly is your firewall going to stop that sort of traffic? The answer you're searching for is, "it won't."
Ahh but if you are allowing 443/tcp, how exactly is your IDS going to detect that sort of traffic? Seeing how the session is encrypted. The answer you're searching for is, "it won't."