Snort mailing list archives
Re: Question about negated and non-negated variables in rules
From: Matt Kettler <mkettler () evi-inc com>
Date: Fri, 28 Nov 2003 14:12:56 -0500
At 08:49 AM 11/27/2003, J-H. Johansen wrote:
I'm working on some ICMP rules and was wondering Recently I added a variable which contains our homenet with exclusions: var NOT_ICMP_SERVERS [$HOME_NET,!xxx.xxx.xx.xxx/32,!xxx.xx.xx.xx/32] This failed while running a check so I've also tried: Any clues as to how this must be done ?
All of the above rules are logically equivalent to "any". what you really want is: var NOT_ICMP_SERVERS ![$HOME_NET,xxx.xxx.xx.xxx/32,xxx.xx.xx.xx/32] ie: Not (a or b or c) instead of (not a) or (not b) or (not c).Work through the boolean math... c matches (not a) as well as (not b). Thus everything, including a, b and c, will match the second version.
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Current thread:
- Question about negated and non-negated variables in rules J-H. Johansen (Nov 27)
- Re: Question about negated and non-negated variables in rules J-H. Johansen (Nov 27)
- Re: [OT] Question about negated and non-negated variables in rules Matt Kettler (Nov 28)
- Re: Question about negated and non-negated variables in rules Matt Kettler (Nov 28)
- Re: Question about negated and non-negated variables in rules Jens-Harald Johansen (Nov 28)
- Re: Question about negated and non-negated variables in rules Matt Kettler (Nov 28)
- Re: Question about negated and non-negated variables in rules Jens-Harald Johansen (Nov 29)
- Re: Question about negated and non-negated variables in rules Matt Kettler (Dec 01)
- Re: Question about negated and non-negated variables in rules J-H. Johansen (Dec 01)
- Re: Question about negated and non-negated variables in rules Matt Kettler (Dec 01)
- Re: Question about negated and non-negated variables in rules Jens-Harald Johansen (Nov 28)
- Re: Question about negated and non-negated variables in rules J-H. Johansen (Nov 27)