A Brief History of Computer Systems and Computer System Security – Part 2: The Mainframe Era of the 1970s

Welcome to Part Two of our comprehensive lecture series on the history of computer systems and computer system security. In this installment, we delve into the Mainframe Era of the 1970s, a pivotal decade that laid the groundwork for modern computing and security practices.

The Rise of Mainframes in the 1970s

By the 1970s, mainframes, often referred to as “data crunchers,” began to dominate the computing landscape. These large-scale computers were essential for bulk data processing, catering primarily to large organizations and government departments. A significant technological advancement of this era was the introduction of the 70 MB hard drive, a considerable leap in storage capacity at the time.

Mainframes were indispensable for handling vast amounts of data, enabling complex computations and data management tasks. Computer and system security during this period were managed by dedicated professionals, ensuring that these powerful machines operated smoothly and securely. The 1970s also marked the introduction of security measures for military and classified applications, highlighting the growing importance of safeguarding sensitive information.

Key Developments in Computer Security

The 1970s were a transformative period for computer security, characterized by several key contributions:

• Information Flow Models: These models laid the foundation for understanding how information moves within a system, crucial for developing robust authorization mechanisms.
• The 1972 Anderson Report: Commissioned by the US Air Force and chaired by James Anderson, this report addressed unresolved security concerns in commercial operating systems, proposing foundational solutions for system security.
• Saltzer and Schroeder’s Security Design Principles (1975): This seminal work introduced eight principles that continue to influence secure software design today.
• Advances in Cryptography: Notably, Diffie and Hellman’s groundbreaking paper, “New Directions in Cryptography,” introduced public-key cryptography, revolutionizing secure communications.

The 1972 Anderson Report: Securing Commercial Operating Systems

The Anderson Report was a landmark study focused on the security of commercial operating systems for the US Air Force. The central question posed by the report was:

“How could the US Air Force trust the security of commercial operating systems?”

Major Findings

1. User Configurability Issues: The report identified that nearly any user could reconfigure the operating system, allowing malicious actors or even accidental modifications to undermine existing security measures.
2. Infeasibility of Retrofitting Security: Attempting to add security features to existing systems was deemed impractical. Instead, the report advocated for building security from the ground up during system design.

Types of Security Violations

Anderson categorized security violations into three types, aligning with what is now known as the CIA Triad:

1. Confidentiality Breaches: Unauthorized release of information.
2. Integrity Breaches: Unauthorized modification of information.
3. Availability Breaches: Unauthorized denial of access to information.

Formal Security Models and Reference Monitors

A key contribution of the Anderson Report was the introduction of formal security models, which provide guidelines for specifying adversary capabilities and goals. This formalization is crucial for translating security requirements into technical specifications.

The report also introduced the concept of the reference monitor, an abstract entity ensuring that all access requests are validated against authorized permissions. Implemented as part of the security kernel, the reference monitor must be tamper-proof, complete, and verifiable:

• Tamper-Proof: It should be impossible to modify the mechanism.
• Complete: It must always be invoked for every access request.
• Verifiable: It should be simple enough to allow thorough analysis and testing.

Saltzer and Schroeder’s Eight Security Design Principles

In 1975, Saltzer and Schroeder published a groundbreaking paper outlining eight principles for designing secure systems. These principles remain foundational in modern cybersecurity practices:

1. Economy of Mechanism: Keep the design as simple as possible to reduce vulnerabilities and make errors easier to detect.
2. Fail-Safe Defaults: Default to denying access unless explicitly authorized, minimizing the risk of unauthorized access.
3. Complete Mediation: Ensure that every access request is checked against the security policy, preventing unauthorized access.
4. Open Design: Do not rely on obscurity for security; instead, ensure that the system’s security does not depend on the secrecy of its design or implementation.
5. Least Privilege: Grant programs and users the minimum level of access necessary to perform their functions, limiting potential damage from errors or attacks.
6. Least Common Mechanism: Minimize shared resources to reduce the risk of unauthorized access or interference between programs.
7. Separation of Privilege: Use multiple independent checks (e.g., two-factor authentication) to authorize access, enhancing security through redundancy.
8. Ease of Use (Psychological Acceptability): Design security mechanisms that are user-friendly to ensure compliance and reduce the likelihood of workarounds.

Importance of These Principles

Adhering to these principles helps create systems that are not only secure but also maintainable and user-friendly. For instance, implementing sandboxing and trusted execution environments can encapsulate programs within controlled environments, reducing the attack surface. Additionally, hardware advancements like the Intel 80386’s memory protection features demonstrate the integration of these principles at the hardware level.

Advances in Networking and the Late 1970s

The late 1970s also witnessed significant strides in networked computing, with the early development stages of TCP/IP at Stanford University. While the comprehensive history of networking extends beyond this module, it’s essential to acknowledge that these advancements set the stage for the interconnected world we live in today.

Conclusion

By the end of the 1970s, the foundations for implementing robust security features in modern operating systems were well-established. The era of mainframes not only showcased the immense capabilities of large-scale computing but also underscored the critical importance of integrating security from the ground up.

Stay tuned for Part Three of our series, where we will continue exploring the evolution of computer systems and the ever-advancing field of computer system security.