Here,s why:
A). Restricting Inbound Traffic:This significantly reduces the attack surface by limiting potential access points to a narrow set of authorized sources. Even if an attacker compromises a system with allowed access, they,re less likely to be able to exploit the bastion due to the restricted traffic flow.
This adheres to the principle of least privilege by granting access only to those who genuinely need it, minimizing potential vulnerabilities.
B). Disabling SSH and Using Alternative Protocols:While disabling SSH completely might seem secure, it might restrict legitimate access and require alternative solutions that may not be readily available or offer the same level of security. Evaluating alternative protocols like RDP with strong authentication measures can be considered, but the focus should still be on controlling access, not eliminating protocols entirely.
C). Static IP Addresses:While convenient for management, static IP addresses can make them easier to target for attackers. Dynamic IP allocation with proper management practices can enhance security without sacrificing usability.
D). Password-Based Authentication:This is generally considered less secure than other methods like multi-factor authentication (MFA), which adds an extra layer of verification beyond just a password. Password-based access should be avoided if possible, or only used with very strong password policies and frequent rotations.
Therefore, while all security measures have their roles, restricting inbound traffic holds the highest priority in securing a bastion service. It directly addresses the core purpose of a bastion - acting as a controlled entry point - and significantly reduces the potential for unauthorized access.