Hi All,


I’ve been trying for a few days to verify whether or not I’ve got mod_security installed properly by applying a single rule in a virtual host. I’ve been unable to convince myself that it is working. No doubt I am making some kind of stupid newbie configuration mistake. Can you help me out?


I’ve got the recommended “base”  configuration copied from the mod security reference manual (see below) which includes:


SecRuleEngine DetectionOnly


The virtual host configuration is as follows:


# Set Default Action to deny the request and report error "403 Forbidden"

SecDefaultAction "phase:1,deny,log,auditlog,status:403"


# Test Rule – pretend valid requestor IP address is 123.456.789.012

SecRule REMOTE_ADDR "!^123\.456\.789\.012$"


I include the base security configuration in the main body of httpd.conf, and I include virtual hosts configuration within the <VirtualHost>.


When I issue a GET request to the server, the mod security Audit Log remains empty. I would have thought I’d see an error 403 produced.


The Debug Log gives lots of detail which includes several instances of this disheartening message:


This phase consists of 0 rule(s).


Which leads me to believe that the REMOTE_ADDR rule is not being applied.

What am I doing wrong?




# security-base.conf - base mod_security directives.

# ----------------------------------------------------------------------------


# -- Rule engine initialization ----------------------------------------------


# Enable ModSecurity, attaching it to every transaction. Use detection

# only to start with, because that minimises the chances of post-installation

# disruption.


SecRuleEngine DetectionOnly



# -- Request body handling ---------------------------------------------------


# Allow ModSecurity to access request bodies. If you don't, ModSecurity

# won't be able to see any POST parameters, which opens a large security

# hole for attackers to exploit.


SecRequestBodyAccess On



# Enable XML request body parser.

# Initiate XML Processor in case of xml content-type


SecRule REQUEST_HEADERS:Content-Type "text/xml" \




# Maximum request body size we will accept for buffering. If you support

# file uploads then the value given on the first line has to be as large

# as the largest file you are willing to accept. The second value refers

# to the size of data, with files excluded. You want to keep that value as

# low as practical.


SecRequestBodyLimit 13107200

SecRequestBodyNoFilesLimit 131072


# Store up to 128 KB of request body data in memory. When the multipart

# parser reachers this limit, it will start using your hard disk for

# storage. That is slow, but unavoidable.


SecRequestBodyInMemoryLimit 131072


# What do do if the request body size is above our configured limit.

# Keep in mind that this setting will automatically be set to ProcessPartial

# when SecRuleEngine is set to DetectionOnly mode in order to minimize

# disruptions when initially deploying ModSecurity.


SecRequestBodyLimitAction Reject


# Verify that we've correctly processed the request body.

# As a rule of thumb, when failing to process a request body

# you should reject the request (when deployed in blocking mode)

# or log a high-severity alert (when deployed in detection-only mode).


SecRule REQBODY_ERROR "!@eq 0" \

"phase:2,t:none,log,deny,status:400,msg:'Failed to parse request body.',logdata:'%{reqbody_error_msg}',severity:2"


# By default be strict with what we accept in the multipart/form-data

# request body. If the rule below proves to be too strict for your

# environment consider changing it to detection-only. You are encouraged

# _not_ to remove it altogether.



"phase:2,t:none,log,deny,status:44,msg:'Multipart request body \

failed strict validation: \













# Did we see anything that might be a boundary?



"phase:2,t:none,log,deny,status:44,msg:'Multipart parser detected a possible unmatched boundary.'"


# PCRE Tuning

# We want to avoid a potential RegEx DoS condition


SecPcreMatchLimit 1000

SecPcreMatchLimitRecursion 1000


# Some internal errors will set flags in TX and we will need to look for these.

# All of these are prefixed with "MSC_".  The following flags currently exist:


# MSC_PCRE_LIMITS_EXCEEDED: PCRE match limits were exceeded.


SecRule TX:/^MSC_/ "!@streq 0" \

        "phase:2,t:none,deny,msg:'ModSecurity internal error flagged: %{MATCHED_VAR_NAME}'"



# -- Response body handling --------------------------------------------------


# Allow ModSecurity to access response bodies.

# You should have this directive enabled in order to identify errors

# and data leakage issues.


# Do keep in mind that enabling this directive does increases both

# memory consumption and response latency.


SecResponseBodyAccess On


# Which response MIME types do you want to inspect? You should adjust the

# configuration below to catch documents but avoid static files

# (e.g., images and archives).


SecResponseBodyMimeType text/plain text/html text/xml


# Buffer response bodies of up to 512 KB in length.

SecResponseBodyLimit 524288


# What happens when we encounter a response body larger than the configured

# limit? By default, we process what we have and let the rest through.

# That's somewhat less secure, but does not break any legitimate pages.


SecResponseBodyLimitAction ProcessPartial



# -- Filesystem configuration ------------------------------------------------


# The location where ModSecurity stores temporary files (for example, when

# it needs to handle a file upload that is larger than the configured limit).


# This default setting is chosen due to all systems have /tmp available however,

# this is less than ideal. It is recommended that you specify a location that's private.


SecTmpDir /tmp/


# The location where ModSecurity will keep its persistent data.  This default setting

# is chosen due to all systems have /tmp available however, it

# too should be updated to a place that other users can't access.


SecDataDir /tmp/



# -- File uploads handling configuration -------------------------------------


# The location where ModSecurity stores intercepted uploaded files. This

# location must be private to ModSecurity. You don't want other users on

# the server to access the files, do you?


#SecUploadDir /opt/modsecurity/var/upload/


# By default, only keep the files that were determined to be unusual

# in some way (by an external inspection script). For this to work you

# will also need at least one file inspection rule.


#SecUploadKeepFiles RelevantOnly


# Uploaded files are by default created with permissions that do not allow

# any other user to access them. You may need to relax that if you want to

# interface ModSecurity to an external program (e.g., an anti-virus).


#SecUploadFileMode 0600



# -- Debug log configuration -------------------------------------------------


# The default debug log configuration is to duplicate the error, warning

# and notice messages from the error log.


SecDebugLog /usr/local/apache2/logs/modsec_debug.log

SecDebugLogLevel 9



# -- Audit log configuration -------------------------------------------------


# Log the transactions that are marked by a rule, as well as those that

# trigger a server error (determined by a 5xx or 4xx, excluding 404,

# level response status codes).


SecAuditEngine RelevantOnly

SecAuditLogRelevantStatus "^(?:5|4(?!04))"


# Log everything we know about a transaction.



# Use a single file for logging. This is much easier to look at, but

# assumes that you will use the audit log only ocassionally.


SecAuditLogType Serial

SecAuditLog /usr/local/apache2/logs/modsec_audit.log


# Specify the path for concurrent audit logging.

#SecAuditLogStorageDir /opt/modsecurity/var/audit/



# -- Miscellaneous -----------------------------------------------------------


# Use the most commonly used application/x-www-form-urlencoded parameter

# separator. There's probably only one application somewhere that uses

# something else so don't expect to change this value.


SecArgumentSeparator &


# Settle on version 0 (zero) cookies, as that is what most applications

# use. Using an incorrect cookie version may open your installation to

# evasion attacks (against the rules that examine named cookies).


SecCookieFormat 0



My apache is:


Server version: Apache/2.2.20 (Unix)

Server built:   Sep 16 2011 10:16:58

Server's Module Magic Number: 20051115:28

Server loaded:  APR 1.4.5, APR-Util 1.3.12

Compiled using: APR 1.4.5, APR-Util 1.3.12

Architecture:   32-bit

Server MPM:     Prefork

  threaded:     no

    forked:     yes (variable process count)

Server compiled with....

-D APACHE_MPM_DIR="server/mpm/prefork"



-D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)







-D HTTPD_ROOT="/usr/local/httpd-2.2.20"

-D SUEXEC_BIN="/usr/local/httpd-2.2.20/bin/suexec"

-D DEFAULT_PIDLOG="logs/httpd.pid"

-D DEFAULT_SCOREBOARD="logs/apache_runtime_status"

-D DEFAULT_LOCKFILE="logs/accept.lock"

-D DEFAULT_ERRORLOG="logs/error_log"

-D AP_TYPES_CONFIG_FILE="conf/mime.types"

-D SERVER_CONFIG_FILE="conf/httpd.conf"




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