APACHE v1.3
-----------
Without DSO Support:
1. Extract this archive into src/modules in the Apache source tree
2. Run ./configure --add-module=src/modules/evasive/mod_evasive.c
3. make, install
4. Restart Apache
With DSO Support, Ensim, or CPanel:
1. $APACHE_ROOT/bin/apxs -iac mod_evasive.c
2. Restart Apache
APACHE v2.0
-----------
1. Extract this archive
2. Run $APACHE_ROOT/bin/apxs -i -a -c mod_evasive20.c
3. The module will be built and installed into $APACHE_ROOT/modules, and loaded into your httpd.conf
4. Restart Apache
CONFIGURATION
mod_evasive has default options configured, but you may also add the
following block to your httpd.conf:
APACHE v1.3
-----------
<IfModule mod_evasive.c>
DOSHashTableSize 3097
DOSPageCount 2
DOSSiteCount 50
DOSPageInterval 1
DOSSiteInterval 1
DOSBlockingPeriod 10
</IfModule>
APACHE v2.0
-----------
<IfModule mod_evasive20.c>
DOSHashTableSize 3097
DOSPageCount 2
DOSSiteCount 50
DOSPageInterval 1
DOSSiteInterval 1
DOSBlockingPeriod 10
</IfModule>
Optionally you can also add the following directives:
DOSEmailNotify
you@yourdomain.com
DOSSystemCommand "su - someuser -c '/sbin/... %s ...'"
DOSLogDir "/var/lock/mod_evasive"
You will also need to add this line if you are building with dynamic support:
APACHE v1.3
-----------
AddModule mod_evasive.c
APACHE v2.0
-----------
LoadModule evasive20_module modules/mod_evasive20.so
(This line is already added to your configuration by apxs)
DOSHashTableSize
----------------
The hash table size defines the number of top-level nodes for each child's
hash table. Increasing this number will provide faster performance by
decreasing the number of iterations required to get to the record, but
consume more memory for table space. You should increase this if you have
a busy web server. The value you specify will automatically be tiered up to
the next prime number in the primes list (see mod_evasive.c for a list
of primes used).
DOSPageCount
------------
This is the threshhold for the number of requests for the same page (or URI)
per page interval. Once the threshhold for that interval has been exceeded,
the IP address of the client will be added to the blocking list.
DOSSiteCount
------------
This is the threshhold for the total number of requests for any object by
the same client on the same listener per site interval. Once the threshhold
for that interval has been exceeded, the IP address of the client will be added
to the blocking list.
DOSPageInterval
---------------
The interval for the page count threshhold; defaults to 1 second intervals.
DOSSiteInterval
---------------
The interval for the site count threshhold; defaults to 1 second intervals.
DOSBlockingPeriod
-----------------
The blocking period is the amount of time (in seconds) that a client will be
blocked for if they are added to the blocking list. During this time, all
subsequent requests from the client will result in a 403 (Forbidden) and
the timer being reset (e.g. another 10 seconds). Since the timer is reset
for every subsequent request, it is not necessary to have a long blocking
period; in the event of a DoS attack, this timer will keep getting reset.
DOSEmailNotify
--------------
If this value is set, an email will be sent to the address specified
whenever an IP address becomes blacklisted. A locking mechanism using /tmp
prevents continuous emails from being sent.
NOTE: Be sure MAILER is set correctly in mod_evasive.c
(or mod_evasive20.c). The default is "/bin/mail -t %s" where %s is
used to denote the destination email address set in the configuration.
If you are running on linux or some other operating system with a
different type of mailer, you'll need to change this.
DOSSystemCommand
----------------
If this value is set, the system command specified will be executed
whenever an IP address becomes blacklisted. This is designed to enable
system calls to ip filter or other tools. A locking mechanism using /tmp
prevents continuous system calls. Use %s to denote the IP address of the
blacklisted IP.
DOSLogDir
---------
Choose an alternative temp directory
By default "/tmp" will be used for locking mechanism, which opens some
security issues if your system is open to shell users.
Home
In the event you have nonprivileged shell users, you'll want to create a
directory writable only to the user Apache is running as (usually root),
then set this in your httpd.conf.
WHITELISTING IP ADDRESSES
IP addresses of trusted clients can be whitelisted to insure they are never
denied. The purpose of whitelisting is to protect software, scripts, local
searchbots, or other automated tools from being denied for requesting large
amounts of data from the server. Whitelisting should *not* be used to add
customer lists or anything of the sort, as this will open the server to abuse.
This module is very difficult to trigger without performing some type of
malicious attack, and for that reason it is more appropriate to allow the
module to decide on its own whether or not an individual customer should be
blocked.
To whitelist an address (or range) add an entry to the Apache configuration
in the following fashion:
DOSWhitelist 127.0.0.1
DOSWhitelist 127.0.0.*
Wildcards can be used on up to the last 3 octets if necessary. Multiple
DOSWhitelist commands may be used in the configuration.
TWEAKING APACHE
The keep-alive settings for your children should be reasonable enough to
keep each child up long enough to resist a DOS attack (or at least part of
one). Remember, it is the child processes that maintain their own internal
IP address tables, and so when one exits, so does all of the IP information it
had. For every child that exits, another 5-10 copies of the page may get
through before putting the attacker back into '403 Land'. With this said,
you should have a very high MaxRequestsPerChild, but not unlimited as this
will prevent cleanup.
You'll want to have a MaxRequestsPerChild set to a non-zero value, as
DosEvasive cleans up its internal hashes only on exit. The default
MaxRequestsPerChild is usually 10000. This should suffice in only allowing
a few requests per 10000 per child through in the event of an attack (although
if you use DOSSystemCommand to firewall the IP address, a hole will no
longer be open in between child cycles).
TESTING
Want to make sure it's working? Run test.pl, and view the response codes.
It's best to run it several times on the same machine as the web server until
you get 403 Forbidden messages. Some larger servers with high child counts
may require more of a beating than smaller servers before blacklisting
addresses.
Please don't use this script to DoS others without their permission.
Chống HTTP DoS or DDoS attack trong OS linux CentOS
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