The purpose of the isdataat keyword is to look if there is still data
at a specific part of the payload. The keyword starts with a number
(the position) and then optional followed by 'relative' separated by a
-comma and the option rawbytes. You use the word 'relative' to know if
+comma and the option rawbytes. You use the word 'relative' to know if
there is still data at a specific part of the payload relative to the
last match.
alert http any any -> any any (msg:"HTTP request without referer"; :example-rule-emphasis:`http.referer; absent: or_else;` content: !"abc"; sid:1; rev:1;)
-For files (ie ``file.data``), absent means there are no files in the transaction.
+For files (i.e ``file.data``), absent means there are no files in the transaction.
bsize
-----
The ``entropy`` keyword calculates the Shannon entropy value for content and compares it with
an entropy value. When there is a match, rule processing will continue. Entropy values
-are between 0.0 and 8.0, inclusive. Internally, entropy is representing as a 64-bit
+are between 0.0 and 8.0, inclusive. Internally, entropy is represented as a 64-bit
floating point value.
The ``entropy`` keyword syntax is the keyword entropy followed by options
replace
-------
-The replace content modifier can only be used in ips. It adjusts
+The replace content modifier can only be used in IPS. It adjusts
network traffic. It changes the content it follows ('abc') into
another ('def'), see example:
*Pcre compatible modifiers*
There are a few pcre compatible modifiers which can change the
-qualities of pcre as well. These are:
+qualities of pcre as well. These are:
* ``A``: A pattern has to match at the beginning of a buffer. (In pcre
^ is similar to A.)
.. image:: pcre/pcre6.png
* ``I``: Makes pcre match on the HTTP-raw-uri. It matches on the same
- buffer as http_raw_uri. I can be combined with /R. Note that R is
+ buffer as http_raw_uri. I can be combined with /R. Note that R is
relative to the previous match so both matches have to be in the
HTTP-raw-uri buffer. Read more about :ref:`HTTP URI Normalization <rules-http-uri-normalization>`.
/R. Note that R is relative to the previous match so both matches
have to be in the HTTP-response body.
-* ``H``: Makes pcre match on the HTTP-header. H can be combined with
+* ``H``: Makes pcre match on the HTTP-header. H can be combined with
/R. Note that R is relative to the previous match so both matches have
to be in the HTTP-header body.
* ``D``: Makes pcre match on the unnormalized header. So, it matches
- on the same buffer as http_raw_header. D can be combined with
+ on the same buffer as http_raw_header. D can be combined with
/R. Note that R is relative to the previous match so both matches
have to be in the HTTP-raw-header.