From owner-freebsd-amd64@freebsd.org Mon Apr 2 16:47:16 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 208E7F76C4A for ; Mon, 2 Apr 2018 16:47:16 +0000 (UTC) (envelope-from cfaber@gmail.com) Received: from mail-io0-x241.google.com (mail-io0-x241.google.com [IPv6:2607:f8b0:4001:c06::241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 979FA86D27 for ; Mon, 2 Apr 2018 16:47:15 +0000 (UTC) (envelope-from cfaber@gmail.com) Received: by mail-io0-x241.google.com with SMTP id q80so18554842ioi.13 for ; Mon, 02 Apr 2018 09:47:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=g2dXCSGfvMZEsXL3u9lEXNBErdyttrf/eu0+/uQTlTg=; b=fMYQ/uqe6hwntbH839d4mYtSZPDwyyMBGDBFQmWv1DAdQPyETRplqVYa9RfdXcGrwi wY7R5mo1NGHmdKq/Jo8I9QDur3F04DGxDPpj1g2MpoqWQapD6lIPeLymFCRxrwE7TDJc ttXoYRn/QfD5n26d5V6sJWaT+IAa00gsHfUDcw60p+49g/vXKjL7/hlnndyS4xqMsfm9 no7PI0UEkGo8qDqQP2nwUuF1iJ6nmnE6yiCM1tlTznCeJ22Dq+9/+WTf/6h6Rj+JasBp oI6ptH0rGk6MIa9nTHfaZHY4ydkt6mOwXSHL2Hofej9Vvf13nNNUd+p+0f5DIPJ93Gd2 C/yQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=g2dXCSGfvMZEsXL3u9lEXNBErdyttrf/eu0+/uQTlTg=; b=DGHoQdwddabd7Vi7Nz8oo5s0uJJjX3DneUR/xKMS67/hl7D5oiDKzHAR/vmXLbpu6Z sbbh0O77wUXDO/usr8H9ZYXGrpRSWlhMAanm3Q6satUctdYPIAnlOUVNOeDlcGpdsclK PjaTzcDEmicDOvSpbOfSlHNsmB+HIJUfJQxuYzB2xncCBex1DXqR+TfNUywQI2C8474L Qtl1rttnPFh8WhqCQtylZ0ngjxuvCpgjEJ6pfVsW5MS3xSOqev86YlRUC4peDhu5Hv07 6Jj5vdliv/nZgr0XNvQ8TbrYJX50Kr1OiZx8Kcgz9j0AfIuv7m85hrfX+MVlnDdI9leL 2CiA== X-Gm-Message-State: AElRT7G44DckhJZ+Qbiclx4RV4HhsssfwbcfYuWAjK/LRMlPJ0BPyp1w WoDvBkWu4hV3VQsOBmg2t9q1/ga5mRx5nugSNl4= X-Google-Smtp-Source: AIpwx49tAb6TEAqI7dLKBwG2EkIpr4/3Ji5rE/G5cff+dDSjeVfoyJxiWLtX6fsiflNt8KIfbw9rrQoIRKW72RdaFwo= X-Received: by 10.107.199.195 with SMTP id x186mr9346567iof.176.1522687635003; Mon, 02 Apr 2018 09:47:15 -0700 (PDT) MIME-Version: 1.0 References: <20180402155920.GB75445@night.db.net> In-Reply-To: <20180402155920.GB75445@night.db.net> From: Colin Faber Date: Mon, 02 Apr 2018 16:47:04 +0000 Message-ID: Subject: Re: What is the universal (world wide) understanding behind degaussing harddisks? To: Diane Bruce Cc: Turritopsis Dohrnii Teo En Ming , freebsd-amd64@freebsd.org Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.25 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 16:47:16 -0000 2nd, shred with random write 3 pass and zero'd forth pass should be enough for most data recovery efforts. SSDs however are another problem, as they're copy on write devices and are over provisioned to accommodate for failure. In those cases I would consider 9 to 16 full disk random writes with at least 4 zeroing passes, but that still doesn't guarantee the data will not be recoverable. On Mon, Apr 2, 2018, 10:00 AM Diane Bruce wrote: > 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 > _______________________________________________ > freebsd-amd64@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-amd64 > To unsubscribe, send any mail to "freebsd-amd64-unsubscribe@freebsd.org" >