### Configuring the Proxy Server: 1. **Install Squid Proxy Server**:   ```bash   sudo apt update   sudo apt install squid   ``` 2. **Configure Access Control for group1**:   - Allow users in group1 to access any enterprise services:    ```bash    sudo nano /etc/squid/squid.conf    ```    Add the following ACL and http_access lines:    ```plaintext    acl group1_users proxy_auth "/etc/squid/group1_users"    http_access allow group1_users    ``` 3. **Configure Access Control for group2**:   - Allow users in group2 to access only the monitoring system:    ```plaintext    acl group2_users proxy_auth "/etc/squid/group2_users"    http_access allow group2_users monitoring_system    ``` 4. **Deny Access for group3 and Unauthenticated Users**:   - Deny access for users in group3 and unauthenticated users:    ```plaintext    acl group3_users proxy_auth "/etc/squid/group3_users"    http_access deny group3_users    http_access deny !proxy_auth    ``` 5. **Configure Internet and Enterprise Service Access for CLI-HQ**:   - Allow CLI-HQ users to access the Internet and all enterprise services except specified domains:    ```plaintext    acl cli_hq_computers src <CLI-HQ-IP>/32    acl blocked_domains dstdomain ..vk.com..mail.yandex.ru..worldskills.org   http_access allow cli_hq_computers !blocked_domains    ``` 6. **Configure Client PC to Use the Enterprise Proxy Server**:   - Configure the client PC to use the enterprise proxy server for web traffic. 7. **Restart Squid Service**:   ```bash   sudo systemctl restart squid   ```