如图，有时候我们检查Apache日记的时候会发现大量这样的单IP或多IP在短时间内请求大量不存在的目录/文件，Apache返回404状态，这不仅消耗服务器资源还可能有安全隐患。我们可以通过CSF防火墙解决，CSF可以根据返回状态次数来屏蔽请求IP访问，相关设置和说明：

# This option will keep track of the number of "File does not exist" errors in

# HTACCESS_LOG. If the number of hits is more than LF_APACHE_404 in LF_INTERVAL

# seconds then the IP address will be blocked

#

# Care should be used with this option as it could generate many

# false-positives, especially Search Bots (use csf.rignore to ignore such bots)

# so only use this option if you know you are under this type of attack

#

# A sensible setting for this would be quite high, perhaps 200

#

# To disable set to "0"

LF_APACHE_404 = "200"

# If this option is set to 1 the blocks will be permanent

# If this option is > 1, the blocks will be temporary for the specified number

# of seconds

LF_APACHE_404_PERM = "3600"