Full Disclosure mailing list archives
Re: IDS Signatures
From: Valdis.Kletnieks () vt edu
Date: Tue, 22 Feb 2005 12:19:16 -0500
On Tue, 22 Feb 2005 09:36:21 GMT, preeth k said:
I am designing a Network Intrusion Detection System in Linux. I want to create a database of intrusion signatures using MySQL database. Can anyone please give an idea about what all fields I have to include, how to store packet payload, which pattern matching algorithm to use, etc. (Will Boyer-Moore algorithm be appropriate for pattern matching in IDS?)
Welcome to Systems Analysis 101. ;) I'm sure somebody will provide a pointer to SNORT, which is a good and useful tool. However, it sounds like you want to design your own, which means you have to do your own design work. And you really need to do your requirements list *first*. For instance, the exact fields you need to store in your MySQL database will depend on what things you do or don't think are important to track. Which pattern matching algorithm to use will depend on what you want to support - if all you want to do is "compare for fixed text at a fixed offset", you can probably steal the code from tcpdump that handles expressions like 'ip[0] & 0xf != 5' to catch packets with IP options. If you want to handle full regular expressions at arbitrary offsets, you'll need a more cabable library. So for the 'Boyer-Moore' question - it depends. Do you intend to support features that Boyer-Moore is fast/efficient at? If so, then it's probably appropriate. If you're not offering those features, some other algorithm that's smaller/faster may be a better choice. You may even want a hybrid approach, where you use Boyer-Moore if the signature can use it, and some other algorithm if the other one is a better choice, chosen at runtime....
Attachment:
_bin
Description:
_______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html
Current thread:
- IDS Signatures preeth k (Feb 22)
- RE: IDS Signatures Micheal Espinola Jr (Feb 22)
- Re: IDS Signatures Valdis . Kletnieks (Feb 22)
- Re: IDS Signatures John Galt (Feb 24)
- Re: IDS Signatures Frank Knobbe (Feb 24)
- Re: IDS Signatures John Galt (Feb 24)
- <Possible follow-ups>
- RE: IDS Signatures Michael Scheidell (Feb 22)