A complete CC attack protection strategy includes the following steps:
1. Adjust kernel parameters
In the CentOS 7 system, you can increase the system's resistance to CC attacks by modifying kernel parameters. The specific operation is as follows:
(1) Open the sysctl.conf file:
```
vim /etc/sysctl.conf
```
(2) Add the following configuration at the end of the file:
```
# Increase the maximum number of queued connections on the port
net.ipv4.tcp_max_syn_backlog = 65536
# Enable TCP Cookies protection
net.ipv4.tcp_syncookies = 1
# Enable route filtering
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1
# Modify the number of TCP SYN retries
net.ipv4.tcp_syn_retries = 3
# Strengthen the protection mechanism of TCP connection
net.ipv4.tcp_abort_on_overflow = 1
# Enable TCP timestamp
net.ipv4.tcp_timestamps = 1
# Initial value of new connection
net.ipv4.tcp_slow_start_after_idle = 0
# Timeout setting
net.ipv4.tcp_fin_timeout = 30
net.ipv4.tcp_keepalive_time = 120
net.ipv4.tcp_keepalive_probes = 5
net.ipv4.tcp_keepalive_intvl = 15
# The number of TCP connections allowed to open
net.ipv4.tcp_max_orphans = 327680
```
(3) After saving and closing the file, execute the following command to make the configuration take effect:
```
sysctl -p
```
2. Install firewall software
The CentOS 7 system comes with firewall software FirewallD, which can be installed and started with the following commands:
```
yum install firewalld
systemctl start firewalld
systemctl enable firewalld
```
3. Configure FirewallD
(1) View the default firewall area:
```
firewall-cmd --get-default-zone
```
(2) Add firewall whitelist:
```
firewall-cmd --permanent --zone=public --add-rich-rule='rule family="ipv4" source address="1.2.3.4" reject'
```
(3) Enable firewall CC protection:
```
firewall-cmd --permanent --zone=public --add-rich-rule 'rule protocol="tcp" port="80" ratelimit-burst="1000" ratelimit-seconds="50" reject'
```
(4) Reload the firewall configuration:
```
firewall-cmd --reload
```
4. Install Nginx reverse proxy server
(1) Install Nginx
```
yum install nginx
```
(2) Start Nginx
```
systemctl start nginx
```
(3) Set Nginx to start automatically at boot
```
systemctl enable nginx
```
5. Configure Nginx reverse proxy to limit CC attacks
(1) Open the Nginx configuration file
```
vim /etc/nginx/nginx.conf
```
(2) Add the following configuration in the http section:
```
# Enable limit_req module
limit_req_zone $binary_remote_addr zone=one:10m rate=1r/s;
# Define the limit of Nginx transmission level
limit_req_zone $binary_remote_addr zone=one:10m rate=100r/s;
# Configure limit rules
limit_req zone=one burst=10 nodelay;
```
(3) After saving and closing the file, execute the following command to make the configuration take effect:
```
systemctl restart nginx
```
To sum up, configuring a complete CC attack protection strategy through the above steps can effectively improve the system's ability to withstand pressure and ensure system security and stability.