CISSP 9.3 - Assess & Mitigate Vulnerabilities of Security Architectures (Part 2 of 3)

This episode of the ISC2 Certified Information Systems Security Professional (CISSP) exam prep series continues the Domain 3 tour of hardware, turning to memory and storage. It walks through the memory hierarchy from chips burned at the factory to the drives that hold data for years — and why understanding the physical media is what lets you protect the secrets living inside it.

Frequently Asked Questions

What is read-only memory and its programmable cousins?

Read-only memory holds contents the system can read but not change, burned in at the factory, which makes it ideal for the startup instructions a machine runs before loading its operating system. Its programmable family adds flexibility: a basic programmable chip is burned once by the end user and then locked, an ultraviolet erasable version is wiped with a special light, and an electrically erasable version uses voltage on its pins. Flash memory extends that last idea, erasing in blocks rather than single bytes, which is why it powers memory cards, thumb drives, and solid-state drives.

What is the difference between dynamic and static RAM?

Dynamic memory stores bits in tiny capacitors that leak charge, so the processor must constantly refresh them, which makes it cheaper. Static memory uses switch-like circuits that hold their state without refresh, running faster but costing more. Designers blend the two to balance speed against price, and because all RAM is volatile, critical data must always have a backup elsewhere.

How do secondary and virtual memory extend the system?

Secondary memory is longer-term storage, the magnetic, optical, and flash media the processor cannot touch directly, so the operating system first reads that data into working memory. Virtual memory stretches the addressable space using a swap file on disk, pulling paged-out data back into real memory through a process called paging. The catch is speed: more physical memory reduces the need for paging, and fast flash media softens the penalty when it happens.

How do we classify storage devices?

Three contrasts capture it. Primary storage is the working memory kept close to the processor, while secondary storage is long-term media like drives, tapes, and discs. Volatile devices lose their contents when power is cut while nonvolatile ones retain data, and random access media let you jump straight to any location by address while sequential media, like magnetic tape, force you to pass everything before the spot you want.

What memory security issues must you guard against?

Any device that might retain sensitive data should be purged before it leaves your control, especially storage media and the read-only memory family designed to keep data through power loss. Even volatile working memory can briefly hold its charge after shutdown. A cold boot attack exploits this by freezing memory chips to slow the fade of resident data and lift secrets like encryption keys.

Reference: This article is based on concepts discussed in CISSP 9.3 - Assess & Mitigate Vulnerabilities of Security Architectures (Part 2 of 3).