It creates a giant temporary file that fills the entire free space, writes patterns over it, then deletes it. Rinse and repeat based on the selected passes (1–7, with Guttmann being a paranoid myth for modern drives).
In the digital age, the concept of "deleting" a file is one of the most misunderstood aspects of computing. Many users believe that when they drag a file to the Recycle Bin and empty it, the data is gone forever. In reality, the operating system has simply marked that space as "available," leaving the actual data intact on the hard drive until it is overwritten by new information. This is where tools like CCleaner and its "Wipe Free Space" feature become essential for privacy and security. ccleaner free space wipe
The only way to securely erase an SSD is ATA Secure Erase or encryption + discarding the key. It creates a giant temporary file that fills