From owner-freebsd-amd64@freebsd.org Mon Apr 2 15:59:25 2018 Return-Path: Delivered-To: freebsd-amd64@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 1205EF73DC4 for ; Mon, 2 Apr 2018 15:59:25 +0000 (UTC) (envelope-from db@db.net) Received: from diana.db.net (unknown [IPv6:2620:64:0:1:223:7dff:fea2:c8f2]) by mx1.freebsd.org (Postfix) with ESMTP id 9A6A784A6D for ; Mon, 2 Apr 2018 15:59:24 +0000 (UTC) (envelope-from db@db.net) Received: from night.db.net (localhost [127.0.0.1]) by diana.db.net (Postfix) with ESMTP id 038C82AA371; Mon, 2 Apr 2018 09:49:44 -0600 (MDT) Received: by night.db.net (Postfix, from userid 1000) id D6F0F39813; Mon, 2 Apr 2018 11:59:20 -0400 (EDT) Date: Mon, 2 Apr 2018 11:59:20 -0400 From: Diane Bruce To: Turritopsis Dohrnii Teo En Ming Cc: freebsd-amd64@freebsd.org Subject: Re: What is the universal (world wide) understanding behind degaussing harddisks? Message-ID: <20180402155920.GB75445@night.db.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-BeenThere: freebsd-amd64@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: Porting FreeBSD to the AMD64 platform List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 02 Apr 2018 15:59:25 -0000 On Mon, Apr 02, 2018 at 09:46:05PM +0800, Turritopsis Dohrnii Teo En Ming wrote: > Good evening from Singapore! > > The foremost question which I want to ask is, what is the universal > (world wide) understanding behind degaussing hard drives? If you degauss a modern drive you will make it totally useless to use. You might as well quarter the drive with a bandsaw and incinerate. (This was the recommended procedure for security disks from a (fictitious) agency I worked (indirectly) for years ago.) The problem is modern drives lay down servo tracks on the platters which can only be done at the factory. > > (1) Very very simple 1-pass data wiping, quickest > > a. Using "sudo dd if=/dev/zero of=/dev/sda", overwriting harddisks ... > > b. Using "sudo dd if=/dev/urandom of=/dev/sda", overwriting harddisks Any method you use will *not* remove all data due to the slight wobble of the track due to temperature changes in the disk, vibration all sorts of problems. However at that point if done properly it would take specialized gear only (fictitious) security agencies such as the NSA (fictitious company) would be likely to bother with. The TL;DR answer is. If you want to use the drives afterwards don't simply demagnetize them; A triple write is probably sufficient if it is merely company data. if the data is drug dealings or state secrets then destroy the drives. ;) > Mr. Turritopsis Dohrnii Teo En Ming > Systems and Network Engineer > Republic of Singapore > 2nd April 2018 Monday 9:35 PM Singapore Time GMT+8 -- - db@FreeBSD.org db@db.net http://www.db.net/~db