Paket Filtering (string)
 

Hi All,
I have to implement a content filtering system (string's basically) on a Linux gateway... Basically I don't want some packets (mached by string's) to pass the gateway... Could any one suggest me some open source for that... It should be light weight...

Any help in this regard will be appreciated...

thanks,
ANU

If it's protocol layer stuff like HTTP or P2P you're after you could search the web for "iptables L7 filter". Like mentioned in the other thread, iptables has string match support but I guess it will be slower and more CPU intensive compared to Snort, so maybe you could tell us the reasons why you want this and add a few examples?

Hi,
See like on the gateway I have a user interface which asks a user to block certain type of content (sex, porn, .ocx, .java etc.)... So I need to accomplish it... I am using kernel 2.6.9... I looked for patch-o-matic from netfilter but it doesn't work with kernel 2.6.x... I know kernel 2.6.14 has some string matching cababilities, but I have to stic to the kernel 2.6.9 only... And you were also refering to snort, but at a first look I came to know that it requires some MySQL, Webserver, ACID, webmin... Actully I need to avoid overhead of DB server, webserver... If Snort can work without these then please let me know... There is another one modsecurity but that also requires an APACHAE engine...

thanks and regards,
ANU

What about a squid proxy server?

Hey,
I thought SQUID is basically used for chaching... Can I use SQUID just for filtering the content ? ... and I feel SQUID filters the content, when requested by the browsers... I need filtering as it passes from the gateway...

thanks

Yeah it only filters the web browser, sorry I didn't realise you need for everything going through the gateway.

I know kernel 2.6.14 has some string matching cababilities, but I have to stic to the kernel 2.6.9 only...
I would like you to seriously consider upgrading the kernel before you do anything else. 2.6.9 is way old and contains more vulnerabilities than a sieve. If you really have compelling reasons not to upgrade you will have to spend time researching if mitigating risks is possible at all. This means researching (CVE, http://nvd.nist.gov/nvd.cfm) which vulnerabilities are remotely exploitable, then find any fixes, then lessening risks by compiling a custom 2.6.9 kernel that does include fixes and then test if it's still vulnerable. If the box allows for public access then you will have to do the same for locally exploitable vulns if you can't migrate public access services to another box. I estimate this will cost you considerable time which you should see as a compelling argument to override reasons not to upgrade the kernel (if possible).


And you were also refering to snort, but at a first look I came to know that it requires some MySQL, Webserver, ACID, webmin... Actully I need to avoid overhead of DB server, webserver... If Snort can work without these then please let me know
Management tools can be run from another box. Snort will run OK w/o any.

Thanks boss...