{"id":31743,"date":"2026-10-07T11:53:30","date_gmt":"2026-10-07T09:53:30","guid":{"rendered":"https:\/\/mu.wedoback.com\/?page_id=31743"},"modified":"2026-10-07T12:22:41","modified_gmt":"2026-10-07T10:22:41","slug":"what-is-an-immutable-backup","status":"publish","type":"page","link":"https:\/\/mu.wedoback.com\/en\/guides\/backup\/what-is-an-immutable-backup\/","title":{"rendered":"What is an immutable backup?"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-page\" data-elementor-id=\"31743\" class=\"elementor elementor-31743 elementor-31554\" data-elementor-post-type=\"page\">\n\t\t\t\t<div class=\"elementor-element elementor-element-72f124a e-con-full wdb-g e-flex e-con e-parent\" data-id=\"72f124a\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t<div class=\"elementor-element elementor-element-5815f13 e-con-full wdb-g-hero e-flex e-con e-parent\" data-id=\"5815f13\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t<div class=\"elementor-element elementor-element-f6fa644 e-con-full wdb-g-hero-in e-flex e-con e-parent\" data-id=\"f6fa644\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-ee00e0c elementor-widget elementor-widget-text-editor\" data-id=\"ee00e0c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p class=\"wdb-g-crumb\"><a href=\"\/en\/\">Home<\/a><span>\u203a<\/span><a href=\"\/en\/guides\/\">Guides<\/a><span>\u203a<\/span><a href=\"\/en\/guides\/backup\/\">IT backup<\/a><\/p><p class=\"wdb-g-pill\" style=\"--pill:#01adb9\">IT backup<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-2453d12 elementor-widget elementor-widget-heading\" data-id=\"2453d12\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h1 class=\"elementor-heading-title elementor-size-default\">What is an immutable backup?<\/h1>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-a15de16 elementor-widget elementor-widget-text-editor\" data-id=\"a15de16\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p class=\"wdb-g-lead\">An immutable backup is a copy that nobody can modify or delete before the end of a set period: not the user, not the administrator, and not an attacker who has stolen their credentials. When the period ends, the copy can expire or be renewed; until then, it remains read-only.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-f65089f elementor-widget elementor-widget-text-editor\" data-id=\"f65089f\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p class=\"wdb-g-meta\"><span>Updated <b>October 2026<\/b><\/span><span><b>3 min<\/b> read<\/span><span><b>4<\/b> sources cited<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-c55b133 e-con-full wdb-g-body e-flex e-con e-parent\" data-id=\"c55b133\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t<div class=\"elementor-element elementor-element-86a4089 e-con-full wdb-g-grid e-flex e-con e-parent\" data-id=\"86a4089\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t<div class=\"elementor-element elementor-element-87c013b e-con-full wdb-g-article e-flex e-con e-parent\" data-id=\"87c013b\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-1eaa203 elementor-widget elementor-widget-text-editor\" data-id=\"1eaa203\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<div class=\"wdb-g-key\"><h2>Key points<\/h2><ul><li>Immutability is enforced <strong>by the storage itself<\/strong>, not by a setting the administrator could untick.<\/li><li>It protects copies against deletion by ransomware or a stolen account, but replaces neither encryption, nor antivirus, nor restore tests.<\/li><li>Against ransomware, the usual target is 30 to 90 days; for a legal obligation, the period set by the law, applied only to the documents concerned.<\/li><li>The ANSSI, France&#8217;s national cybersecurity agency, recommends keeping at least one offline copy: immutability is its logical equivalent for a copy that stays online.<\/li><\/ul><\/div>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d4ec2c4 elementor-widget elementor-widget-text-editor\" data-id=\"d4ec2c4\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>Why immutability exists<\/h2><p>Standard backups remain files that the backup software is able to delete. This is useful to avoid filling up the storage. It is also exactly what ransomware does when it takes control of the console: delete the copies before encrypting production, leaving no choice but to pay. Immutability moves the decision: deletion is refused <strong>by the storage itself<\/strong> for N days, not by a checkbox the administrator can untick.<\/p><p>It also serves as proof. An accounting document or a record that must be produced unaltered cannot live on a volume where any operator can rewrite the history.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-ea56ae4 elementor-widget elementor-widget-text-editor\" data-id=\"ea56ae4\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>Immutable, offline, standard: three levels of protection<\/h2><p>The ANSSI recalls the so-called \u201c3-2-1\u201d rule: three copies of the data, on two different media, one of which is offline. The offline copy remains the safest defence against ransomware, because no connected account can reach it. The immutable copy plays the same role for a backup that must stay online, and therefore quick to restore.<\/p><table><thead><tr><th><\/th><th>Standard backup<\/th><th>Immutable backup<\/th><th>Offline copy<\/th><\/tr><\/thead><tbody><tr><td>Deletion by an administrator<\/td><td>Possible<\/td><td>Refused until expiry<\/td><td>Impossible without physical access<\/td><\/tr><tr><td>Resistance to a stolen account<\/td><td>Low<\/td><td>High<\/td><td>High<\/td><\/tr><tr><td>Restoration speed<\/td><td>High<\/td><td>High<\/td><td>Slower (media to be retrieved)<\/td><\/tr><tr><td>Discipline required<\/td><td>Low<\/td><td>Low<\/td><td>Regular media rotation<\/td><\/tr><\/tbody><\/table>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-1975741 elementor-widget elementor-widget-text-editor\" data-id=\"1975741\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>What immutability is not<\/h2><ul><li><strong>It is not encryption.<\/strong> Encryption prevents reading without the key. It does not prevent deletion.<\/li><li><strong>It is not retention.<\/strong> Retention says \u201cwe keep 30 days\u201d. If the administrator can shorten that period or purge, it is not immutable.<\/li><li><strong>It is not antivirus.<\/strong> Production can still be encrypted. Immutability is there to recover an earlier version.<\/li><li><strong>It is not instantaneous.<\/strong> The immutable copy is as old as the last successful backup. If the last clean copy dates from the previous day, you lose a day&#8217;s work.<\/li><\/ul>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-eeb55b4 elementor-widget elementor-widget-text-editor\" data-id=\"eeb55b4\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>How to implement it<\/h2><p>The most widespread mechanism is called WORM: <em>write once, read many<\/em>. You write once, read as often as you like, and never overwrite. Cloud object storage and some NAS devices offer object locking. The lock must still not be liftable by the same account as production, and the period must exceed the time needed to discover the attack.<\/p><p>Three points to check before choosing a solution:<\/p><ol><li><strong>Who can lift the lock?<\/strong> In \u201ccompliance\u201d mode, nobody before expiry. In \u201cgovernance\u201d mode, a privileged account can: that account must then be protected like the rest of the backup infrastructure.<\/li><li><strong>Are actions logged?<\/strong> A refused deletion request is a valuable warning sign.<\/li><li><strong>Is the backup console isolated from production?<\/strong> The ANSSI recommends dedicated, named administration accounts, and backup servers that do not join the production directory.<\/li><\/ol><p>A tape removed from the drive and stored off site is a physical form of immutability, provided someone actually carries out the rotation.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-2e4d595 elementor-widget elementor-widget-text-editor\" data-id=\"2e4d595\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>Useful period<\/h2><p>Against ransomware: often 30 to 90 days, sometimes more if detection is slow, because an intrusion can remain unnoticed for several weeks before encryption. For a legal retention obligation: the period set by the applicable law (in Mauritius, for accounting and tax records, the Income Tax Act 1995 and the Companies Act: have it confirmed by your accountant), applied only to the documents concerned, not to the full server image every night. The details are in <a href=\"\/en\/guides\/backup\/immutable-backup-retention-period\/\">Immutable backup: how long should data be kept?<\/a>.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-961170d elementor-widget elementor-widget-text-editor\" data-id=\"961170d\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<div class=\"wdb-g-brand\"><h2>At WeDoBack<\/h2><p>The IMMUTABLE offer relies on WORM storage. For the chosen period, up to ten years, data can be neither modified nor deleted, even if console access were stolen. Every action, including an attempted deletion by an administrator, is logged and the log cannot be erased. The public price is \u20ac20 excl. VAT per 100 GB block per month, plus one agent per machine. The offer can be taken out on its own or in addition to a <a href=\"\/en\/smart-offer\/\">SMART<\/a> or <a href=\"\/en\/integral-offer\/\">INTEGRAL<\/a> backup. At expiry, simply subscribe again to start a new protection period. The encryption key stays with the client: immutability guarantees that the copy is not altered, but you still need to keep the key to be able to read it.<\/p><div class=\"wdb-g-btns\"><a class=\"wdb-g-btn wdb-g-btn-primary\" href=\"\/en\/immutable-offer\/\">Discover the IMMUTABLE offer<\/a><a class=\"wdb-g-btn wdb-g-btn-ghost\" href=\"\/en\/quotation\/\">Request a quote<\/a><\/div><\/div>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-0fe5b83 elementor-widget elementor-widget-text-editor\" data-id=\"0fe5b83\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<div class=\"wdb-g-faq\"><h2>Frequently asked questions<\/h2><details><summary>Can ransomware encrypt an immutable backup?<\/summary><p>No, as long as the lock period is running: the storage refuses any overwrite. However, if the ransomware encrypted production <strong>before<\/strong> the last backup, that copy contains files that are already encrypted. Hence the value of keeping several versions and being able to go back to a date before the attack.<\/p><\/details><details><summary>Can an administrator shorten the immutability period?<\/summary><p>In a true WORM mode known as \u201ccompliance\u201d, no: neither the administrator nor the provider can lift the lock before it expires. Some products offer a \u201cgovernance\u201d mode in which a privileged account can lift it; this mode protects against mistakes, not against an attacker who has stolen that account.<\/p><\/details><details><summary>Should all your backups be made immutable?<\/summary><p>Rarely. Immutability is reserved for data whose loss would be critical or which must be kept unaltered. The rest of the estate can stay on standard backup with history, which costs less and remains more flexible.<\/p><\/details><\/div>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-b4a7d00 elementor-widget elementor-widget-text-editor\" data-id=\"b4a7d00\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>Further reading<\/h2><div class=\"wdb-g-related\"><a href=\"\/en\/guides\/backup\/what-is-worm-storage\/\"><small>IT backup<\/small>What is WORM storage?<\/a><a href=\"\/en\/guides\/backup\/protect-backups-from-ransomware\/\"><small>IT backup<\/small>How to protect your backups from ransomware<\/a><a href=\"\/en\/guides\/backup\/backup-vs-archiving\/\"><small>IT backup<\/small>What is the difference between backup and archiving?<\/a><a href=\"\/en\/guides\/what-to-do-if\/ransomware-just-struck\/\"><small>What to do if\u2026<\/small>Ransomware has just been triggered<\/a><\/div>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-979b272 elementor-widget elementor-widget-text-editor\" data-id=\"979b272\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<div class=\"wdb-g-sources\"><h2>Sources<\/h2><p class=\"wdb-g-src-date\">Documents consulted in October 2026.<\/p><ol><li><a href=\"https:\/\/messervices.cyber.gouv.fr\/documents-guides\/anssi_fondamentaux_sauvegarde_systemes_dinformation_v1.1.pdf\" target=\"_blank\" rel=\"noopener\">Information system backup \u2013 The fundamentals (ANSSI-BP-100, v1.1, 27 November 2025)<\/a> \u2014 ANSSI, France&#8217;s national cybersecurity agency<\/li><li><a href=\"https:\/\/cert-mu.govmu.org\/cert-mu\/wp-content\/uploads\/2023\/10\/Guideline-on-Ransomware-Removal.pdf\" target=\"_blank\" rel=\"noopener\">Guideline on Ransomware Removal<\/a> \u2014 CERT-MU<\/li><li><a href=\"https:\/\/www.mra.mu\/download\/ITAConsolidated.pdf\" target=\"_blank\" rel=\"noopener\">Income Tax Act 1995 (consolidated version)<\/a> \u2014 Mauritius Revenue Authority<\/li><li><a href=\"https:\/\/www.wedoback.com\/offre-immuable\/\" target=\"_blank\" rel=\"noopener\">IMMUTABLE offer: WORM storage and prices<\/a> \u2014 WeDoBack<\/li><\/ol><\/div>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-f13f922 e-con-full wdb-g-aside e-flex e-con e-parent\" data-id=\"f13f922\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-bd23688 elementor-widget elementor-widget-text-editor\" data-id=\"bd23688\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<nav class=\"wdb-g-toc\" aria-label=\"Table of contents\"><p>On this page<\/p><ol><\/ol><\/nav>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-0319289 elementor-widget elementor-widget-text-editor\" data-id=\"0319289\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<div class=\"wdb-g-card\"><h3>Planning a backup, DRP or BCP project?<\/h3><p>More than 20 years of experience protecting business data.<\/p><a class=\"wdb-g-btn wdb-g-btn-primary\" href=\"\/en\/quotation\/\">Request a quote<\/a><a class=\"wdb-g-tel\" href=\"tel:+33972507828\">+33 9 72 50 78 28<\/a><\/div>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-4123096 e-con-full wdb-g-cta e-flex e-con e-parent\" data-id=\"4123096\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t<div class=\"elementor-element elementor-element-c583d9c e-con-full wdb-g-cta-in e-flex e-con e-parent\" data-id=\"c583d9c\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-a0abc5d elementor-widget elementor-widget-text-editor\" data-id=\"a0abc5d\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h2>Protect your data with WeDoBack<\/h2><p>Encrypted offsite backup, immutable storage, DRP and BCP: tell us about your servers and we will recommend the right combination.<\/p><div class=\"wdb-g-btns\"><a class=\"wdb-g-btn wdb-g-btn-primary\" href=\"\/en\/quotation\/\">Request a quote<\/a><a class=\"wdb-g-btn wdb-g-btn-ghost\" href=\"\/en\/offers-and-prices\/\">See offers and prices<\/a><\/div>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"parent":31721,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"elementor_header_footer","meta":{"_seopress_titles_title":"Immutable backup: definition and limits | WeDoBack","_seopress_titles_desc":"An immutable backup cannot be modified or deleted for a set period, even by an administrator. 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