MediaTools Wipe 1.2 has so many handy features (user-definable erase patterns, smart handling of bad blocks, and so on) that I can't mention them all here. Check out our review of the functionally equivalent version 1.1. You'll likely dedicate a PC to it, so the $49, single-seat technician's license will suffice for most situations. However, $500 single-site and $1000 multi-site licenses are available for the corporate crowd.
The handy and free Eraser 6 utility deletes files, folders, and free space on a schedule. It's just the thing for users who want to maintain a minimal data presence on their PC. You must know what you need to erase, since Eraser 6 doesn't have automatic selection of sensitive data, as O&O SafeErase and PrivaZer do. But Eraser 6 does have a large array of government-level algorithms to choose from, and it's super-simple to use.
Active@ KillDisk is available in a free Windows edition and a DOS (boot disc) edition. Either will overwrite free space or entire partitions with a single pass of zeroes. To obtain its more advanced features and algorithms, you'll need the Active@ KillDisk Pro, which costs $40 for Windows, and $50 with the pro-DOS version thrown in. KillDisk won't invoke a disk's secure-erase routine, and it doesn't have any smarts: It doesn't detect and delete sensitive data such as browsing records, downloads, and program caches.
Active@ KillDisk is very effective as far as it goes, but most users will be just as well off with the free Eraser 6 — or better off by paying less for a program that automatically selects and deletes sensitive data and wipes free space. Then again, if you run Piriform's CCleaner before KillDisk (or Eraser 6), you'll have a very effective data-killing combo.
Wiping SSDs and USB Flash drives
Block-overwrite software isn't reliable with NAND-based media because of the voodoo that flash-storage controllers use when writing and deleting data. Im sorry I can't be more specific about what actually happens, but controller vendors are loath to talk about such things, lest they give away a competitive advantage.
That said, SSDs that support the TRIM command and run under a TRIM-supported environment (Windows 7 and 8, OS X 10.6.8 or better, Linux 2.6.28 or better, plus a modern BIOS and drive controller that pass on the command) should wipe deleted data continually. Note that I said "should."
Ideally (for security purposes) an SSD's garbage collection routines, invoked by the TRIM command, would quickly erase the NAND blocks formerly occupied by your file. The whole reason for TRIM is that NAND must be erased before being rewritten. If a drive runs out of clean, unwritten blocks and must erase previously used blocks immediately prior to writing to them, performance suffers drastically.
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