RE: [Snort-sigs] Questions 101

[Matt Kettler <mkettler () evi-inc com>]

Erm, that will look for things web URLS that have spaces that are escaped. 
It will not match the spaces between the text in this email, for example. 
If you want to look for a space character, use content: " ".

Also, binary protocols will contain space characters, but not very often, 
so you could miss many of the packets in the transfer. For example, a 
zipfile or other compressed data could go on for many KB in a row without 
any spaces. It certainly would be unlikely to contain the three characters 
text string: %20

If you really want to log every packet from a given IP, I'd _strongly_ 
recommend that you just drop the content part entirely.  Anything else 
doesn't always do what you want, and wastes CPU time doing an unnecessary 
string search.

There's nothing invalid, or even unusual, about a rule which has no content 
specifier. There are several rules in the snort ruleset that don't have 
them (ie: ones that look for strange flag bits or source IP addresses).


At 03:56 PM 4/3/2003 -0500, you wrote:
> i did a  content:"%20" and the rule works, don't know what it will pick up,
> but I figure everything has a freaking space in it at some point.



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