Yes, if someone knows your public IP address, there are certain security risks, including brute force attacks or flood attempts (DoS or DDoS) against your router or any services you may have exposed to the Internet. Below I describe these risks and how you can protect yourself:

Brute Force Attacks

A brute force attack is performed by trying multiple username and password combinations until the correct one is found to access a system.

If you have services accessible from the Internet (such as SSH, FTP, or web administration panels) and these services are protected only by a username and password, then they are potentially vulnerable to brute force attacks.

Protection:

• Using Strong Passwords: Make sure all accounts have strong, unique passwords.
• Limitation of Access Attempts: Many systems and applications allow you to configure a limit of failed access attempts before temporarily blocking the attacker's IP.
• Two-Factor Authentication (2FA): If possible, enable two-factor authentication to add an extra layer of security.
• Changing Standard Ports: Changing standard ports to less common ones can help prevent automated attacks.

Saturation Attacks (DoS or DDoS)

A Denial of Service (DoS) attack or a Distributed Denial of Service (DDoS) attack seeks to overload your Internet connection or your router's resources, making your online services inaccessible.

Protection:

• Firewall Settings: Make sure your router has properly configured firewall rules to block unwanted or suspicious traffic.
• Connection Rate Limitation: Some routers allow you to configure limitations on the rate of new connections per second from a single source, which can help mitigate DoS attacks.
• DDoS Mitigation Services: For more critical sites or services, consider using DDoS mitigation services offered by specialized security providers.

Other Safety Considerations

• VPN: If you need to access your home or office network from outside, consider setting up a VPN. This hides direct services to the Internet and provides a secure connection.
• Security Updates: Keep your router and any other Internet-connected device up to date with the latest security patches.
• Monitoring: Stay alert for any unusual activity on your network, which may be indicative of an attempted attack or compromise.

It is important to be proactive in securing your network to minimize the risks associated with having a known public IP. Implementing multiple layers of security can help protect your devices and data from unauthorized access and attacks.