Security Basics mailing list archives
RE: Internet filtering at the packet level?
From: "Billy Dodson" <billy () pmm-i com>
Date: Mon, 23 Aug 2004 14:06:28 -0500
If your running linux anyway, you should look into Squid Proxy for linux. It is a Proxy server/Caching engine that runs on linux. http://www.squid-cache.org It has the logging and reporting that I think you might be looking for. -----Original Message----- From: Rob Creely [mailto:programmingart () gmail com] Sent: Saturday, August 21, 2004 5:51 PM To: Will - Security Engine Cc: security-basics () securityfocus com Subject: Re: Internet filtering at the packet level? Any reason you can't just block all outgoing traffic except traffic to your proxy server which is doing the filtering? I think you looking at a lot of overhead and network slowdown by scanning every single packet. How about the people that connect to a secure web proxy via SSL? How about people that use SSH forwarding to a web proxy? You can't examine those packets, they are encypted. Just my 2 cents..... Cheers. --Rob On Tue, 17 Aug 2004 14:51:25 -0500, Will - Security Engine <security () the-engine org> wrote:
Ok, I was wondering if it was feasable to filter internet access at the packet level. Here is the scenario. Small college campus - lets say 500 live on campus. About half that has internet access. Then you also have the computer lab, with 16 computers. Each teacher has a computer in their office as well, and the CIS dept has about 30 or so computers in use. The filtering would be done on a Linux server using TCPDump. I know how to implement flags for content checking (If the phrase "hot monkey
sex"
comes up in a packet, the user is flagged and traffic for that user would be logged for a set period of time for reviewing later). What I
don't know is how to actually stop the traffic - but we won't worry about that for now. Is there any problems with this? Is it feasable? How about just the flagging portion of it, rather than the actual content blocking? I'm a student at a private baptist college that gets it's internet access through MOREnet. They require that we filter the content in order to use their services. Currently we only use a URL keyword and blacklist filtering system (from my own tests), but it's obvious that anybody who is serious about getting around the filter will have no problem (web proxies are stupid easy to set up yourself, and P2P isn't
filtered). I'm worried that at some point it will come up that we aren't doing a good enough job filtering, so we'd need a new solution. I think the packet-based system would be more accurate. I would be more inclined to not actually block the content that gets flagged. I would rather know that the user is accessing content ruled against by the ToS and confront them on the issue. Lets not turn this into a censorship debate please ;) ---------------------------------------------------------------------- ----- Computer Forensics Training at the InfoSec Institute. All of our
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Current thread:
- Internet filtering at the packet level? Will - Security Engine (Aug 20)
- Re: Internet filtering at the packet level? Andreas (Aug 23)
- Re: Internet filtering at the packet level? Rob Creely (Aug 23)
- Re: Internet filtering at the packet level? Brian Kim (Aug 24)
- Re: Internet filtering at the packet level? Gabriel Orozco (Aug 23)
- <Possible follow-ups>
- Re: Internet filtering at the packet level? Will - Security Engine (Aug 23)
- RE: Internet filtering at the packet level? BANIER Jeremie (Aug 23)
- Re: Internet filtering at the packet level? Brian Kim (Aug 25)
- RE: Internet filtering at the packet level? BĂ©noni MARTIN (Aug 23)
- Re: Internet filtering at the packet level? Will - Security Engine (Aug 24)
- RE: Internet filtering at the packet level? Billy Dodson (Aug 24)