CompTIA Exam Prep - ITF+, A+, Network+, Security+, CySA+

Overwriting every addressable sector is a sound way to sanitize a magnetic hard drive and an unreliable way to sanitize a solid state drive. The reason is architectural, not a matter of doing more passes, and understanding it is what separates a correct answer from a confident wrong one. Why overwriting does not reach the data Flash memory cells wear out after a finite number of write cycles, so an SSD controller distributes writes across the whole device to extend its life. The logical block address the operating system writes to is mapped by the controller to whatever physical cell it chooses, and that mapping changes constantly. So when software overwrites logical block 500, the controller writes the new data to a fresh physical cell and marks the old one invalid. The original data is still physically present, just no longer reachable through the normal interface. Over-provisioning compounds this. Drives contain more flash than they advertise — commonly seven to twenty-eig...

Steganography hides the existence of a message. Encryption hides the content . That distinction is the whole topic: encrypted traffic is obviously encrypted and invites attention, while a steganographic payload looks like an ordinary holiday photograph and invites none. The two are complementary, and serious use combines them — encrypt first, then hide the ciphertext. How it works in images The standard technique is least significant bit substitution. A pixel's colour is stored as numeric values, and changing the last bit of each value alters the colour by an amount no eye can perceive. Spread across a photograph's millions of pixels, that yields a substantial hidden payload in a file that looks completely normal. The constraint is the file format. Lossless formats such as PNG and BMP preserve every bit, so the payload survives. Lossy compression recalculates pixel values, which destroys LSB data — so hiding data in a JPEG requires techniques that work within the compre...

Media sanitization is removing data from storage so it cannot be recovered. The standard framework sorts methods into three categories by how much effort recovery would take afterwards, and choosing between them is a risk decision driven by data sensitivity and whether the media is leaving your control. Why deleting is not sanitizing Deleting a file removes its directory entry. The data stays on the medium until something else is written over it, and recovery is a matter of running readily available software. A quick format is the same idea at volume scale — the filesystem structures are rewritten and the data is untouched. A full format on modern systems does write zeros, which is closer to sanitization, but the terminology confuses people and it is not what most users mean when they say they formatted the drive. Emptying the recycle bin, resetting to factory defaults on some devices, and moving files to another volume all leave recoverable data behind. This is the single mo...