Snort performance on Windows XP with SP2

Posted on 2006-06-02
Last Modified: 2013-11-16
Hi Experts,

I want to use SNORT to a personal firewall for windows XP. I have a module that will block the packets but I need a good engine to scan them. My problem is that I have to wait for an answere form snort before I will take any action on the packet(send forward or drop it) and I want to know if the snort is a fast engine that will not decrease veryu much my network performances (actual network speed is about 6 mb/s)

Thank you very much
Question by:aureliuh
    LVL 13

    Expert Comment

    SNORT is as fast as your machine is.

    It can easily look at traffic of about 10Mbps on any normal P4 machine with 512MB RAM.

    We have implemented SNORT in our network of 100Mbps on a server running P4 HT with 1GB of RAM and sata disks. But we are using it for logging network traffic.

    Author Comment

    My problem is that I havedeveloped a personal firewall and it should contain snort too. I have made some tests like, I have generated 5000 rules into the firewall and the result was horibble. The net speed was decreassed to 200 MB (200 *8 - the speed shown by windows).
    LVL 38

    Accepted Solution

    There is a plug-in called SnortSAM that, based on certain alerts you define, can take action against a stream like you describe. I understand you've written your own, so that package my help you intergrate it with snort. SnortSAM will recieve an alert from snort, and update the firewall your using, such as a pix, check-point firewall, ipTables and many more.
        *  Checkpoint Firewall-1
        * Cisco PIX firewalls
        * Cisco Routers (using ACL's or Null-Routes)
        * Former Netscreen, now Juniper firewalls
        * IP Filter (ipf), available for various Unix-like OS'es such as FreeBSD
        * FreeBSD's ipfw2 (in 5.x)
        * OpenBSD's Packet Filter (pf)
        * Linux IPchains
        * Linux IPtables
        * Linux EBtables
        * WatchGuard Firebox firewalls
        * 8signs firewalls for Windows
        * MS ISA Server firewall/proxy for Windows
        * CHX packet filter
        * Ali Basel's Tracker SNMP through the SNMP-Interface-down plugin
        * ...and more to come...

    Snort will impact preformance based on the amount of traffic it has to process through... it's recommended in a high traffic situation, that you dedicate a "sniffer" box to sniff/log the packets and possibly have snortSam or similar product on that same sniffer to update your firewalls. On a cable/DSL or even T1 connection, the preformance hit would not be much on modern hardware (P4 512+ of ram) On a DS3, 100meg and over you'd want to dedicate a box to only sniffing packets.

    If you can write a pre-processor for traffic you want to look at (if a pre-processor doesn't already exist for that type) the impact should be lower. Snort is signature based, and with that in mind, you can't alert on a packet until that signature, threshold or other criteria are matched, and using a "sniffing" box it may be after the fact that the packets get blocked. If you want to block packets before they reach their targets, you have to place snort on the very "edge" of your network to get the best reaction time possible, or to have the packets cached, analysized, then allowed to flow after inspection. Typically snortSam can block a stream before it's too late, things like port scans, P2P connections, viri etc... Things like IIS buffer overflows, if placed they can fit in a single packet, might not stop someone from executing the overflow, however it will stop them from sending/recieving any remaining packets.

    Author Comment

    Thank you very much for your help. it realy helped me!


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