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Example Meaning
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-! 1.1.1.1 Every IP address but 1.1.1.1
+!1.1.1.1 Every IP address but 1.1.1.1
![1.1.1.1, 1.1.1.2] Every IP address but 1.1.1.1 and 1.1.1.2
$HOME_NET Your setting of HOME_NET in yaml
[$EXTERNAL_NET, !$HOME_NET] EXTERNAL_NET and not HOME_NET
If you set your configuration to something like this::
HOME_NET: any
- EXTERNAL_NET: ! $HOME_NET
+ EXTERNAL_NET: !$HOME_NET
- You can not write a signature using ``$EXTERNAL_NET`` because it stands for
- 'not any'. This is an invalid setting.
+ You cannot write a signature using ``$EXTERNAL_NET`` because it evaluates to
+ 'not any', which is an invalid value.
Ports (source and destination)
------------------------------
alert http $HOME_NET :example-rule-emphasis:`any` -> $EXTERNAL_NET :example-rule-emphasis:`any` (msg:"HTTP GET Request Containing Rule in URI"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"rule"; fast_pattern; classtype:bad-unknown; sid:123; rev:1;)
-*The first emphasized part is the source, the second is the destination (note the direction of the directional arrow).*
+*The first emphasized part is the source port, the second is the destination port (note the direction of the directional arrow).*
Traffic comes in and goes out through ports. Different ports have
different port numbers. For example, the default port for HTTP is 80 while 443 is