{"licence":{"name":"CC BY-SA 4.0","spdx":"CC-BY-SA-4.0","url":"https://creativecommons.org/licenses/by-sa/4.0/","attribution":"Atlas, a bilingual technical dictionary (https://cmaintz.github.io/tech-atlas/)"},"id":"security/backup","url":{"en":"https://cmaintz.github.io/tech-atlas/en/terms/security/backup/","da":"https://cmaintz.github.io/tech-atlas/da/terms/security/backup/"},"term":{"en":"Backup","da":"Backup"},"aka":{"en":["backup copy","data backup"],"da":["sikkerhedskopi","sikkerhedskopiering"]},"domain":["security","cs"],"cluster":"controls","layer":"data","status":"current","summary":{"en":"A separate copy of data kept so it can be restored after a breakdown, a mistake or an attack.","da":"En separat kopi af data, som gemmes, så de kan gendannes efter nedbrud, fejl eller angreb."},"body":{"formal":{"en":"A copy of data and system settings taken on a schedule and stored apart from the original - ideally with at least one copy offline - and regularly tested by actually restoring from it.","da":"En kopi af data og systemindstillinger, der tages efter en fast plan og opbevares adskilt fra originalen - helst med mindst én kopi offline - og som jævnligt testes ved faktisk at gendanne fra den."},"plain":{"en":"Like keeping paper copies of your passport and deeds at a relative's house - if your home burns down, the papers are not lost.","da":"Som at have kopier af pas og skøde liggende hos et familiemedlem - hvis dit hus brænder, er papirerne ikke tabt."},"inPractice":{"en":"Ransomware locks a municipality's file server on a Monday; because last night's copy sat on a disk that was not connected, the IT operations team wipes the server and restores the files by lunchtime.","da":"Ransomware låser en kommunes filserver en mandag; fordi nattens kopi lå på en disk, der ikke var tilsluttet, sletter IT-driften serveren og har gendannet filerne ved frokosttid."},"whyItMatters":{"en":"It is the last line of defence for availability - when everything else fails, a tested copy decides whether the business loses hours or loses everything.","da":"Det er sidste forsvarslinje for tilgængeligheden - når alt andet svigter, afgør en testet kopi, om virksomheden mister timer eller mister alt."}},"deepDive":{"en":"Backup design starts from two numbers agreed with the business: the recovery point objective (RPO, how much data loss in time is tolerable) and the recovery time objective (RTO, how long restoration may take). RPO drives backup frequency and technique - nightly full or incremental jobs, continuous journaling, database transaction-log shipping - while RTO drives the restore path: instant VM recovery from a backup repository, bare-metal restore, or rebuilding from infrastructure-as-code and then restoring data. Classic job types are full, incremental (changes since the last backup of any kind) and differential (changes since the last full); modern systems create \"synthetic fulls\" by merging increments on the repository and use block-level change tracking and deduplication to keep windows short.\n\nThe 3-2-1 rule - three copies, on two different media, one off-site - is often extended to 3-2-1-1-0: one copy offline, air-gapped or immutable, and zero errors in verified restores. Immutability is now the main ransomware defence, because modern ransomware operators deliberately locate and delete backup catalogues, shadow copies and repository credentials before encrypting. Implementations include object storage with WORM retention (for example S3 Object Lock in compliance mode, which even the root account cannot shorten), hardened Linux repositories with immutable file flags, tape rotated off-site, and backup systems in a separate administrative domain with their own MFA-protected credentials. Snapshots on the same storage array, RAID and synchronous replication are not backups: they faithfully replicate deletion, corruption and encryption.\n\nConsistency matters as much as existence. A crash-consistent image of a running database may not start; application-consistent backups quiesce writes (on Windows via VSS writers) or use the database's own dump or log mechanism. SaaS data is a frequent gap - under the shared-responsibility model, providers such as Microsoft 365 guarantee service availability but offer limited retention of user-deleted or maliciously altered data.\n\nNormative anchors: CIS Controls v8 Control 11 (Data Recovery), including an isolated instance of recovery data (Safeguard 11.4) and restore tests of a sample of assets at least quarterly (11.5); ISO/IEC 27002:2022 control 8.13 (information backup); NIS2 Art. 21(2)(c), which lists backup management alongside business continuity and disaster recovery; and GDPR Art. 32(1)(c), the ability to restore availability and access to personal data in a timely manner. Retention also has a data-protection side: backups containing personal data are subject to storage limitation, and erasure requests are usually handled by documented expiry rather than editing old backup sets. The only real evidence a backup works is a timed, documented restore.","da":"Backupdesign begynder med to tal, der aftales med forretningen: recovery point objective (RPO, hvor meget datatab målt i tid der kan accepteres) og recovery time objective (RTO, hvor lang tid gendannelsen må tage). RPO bestemmer hyppighed og teknik - natlige fulde eller inkrementelle job, kontinuerlig journalisering, forsendelse af databasens transaktionslog - mens RTO bestemmer gendannelsesvejen: instant recovery af VM'er direkte fra backup-repositoriet, bare-metal-gendannelse eller genopbygning fra infrastructure-as-code efterfulgt af gendannelse af data. De klassiske jobtyper er fuld, inkrementel (ændringer siden seneste backup af enhver art) og differentiel (ændringer siden seneste fulde); moderne systemer danner \"syntetiske fulde\" backups ved at flette inkrementer på repositoriet og bruger ændringssporing på blokniveau og deduplikering for at holde backupvinduerne korte.\n\n3-2-1-reglen - tre kopier, på to forskellige medier, én uden for huset - udvides ofte til 3-2-1-1-0: én kopi offline, air-gapped eller uforanderlig (immutable), og nul fejl i verificerede gendannelser. Uforanderlighed er i dag det vigtigste værn mod ransomware, fordi moderne ransomwaregrupper bevidst finder og sletter backupkataloger, skyggekopier og adgangsoplysninger til repositorier, før de krypterer. Implementeringer omfatter objektlagring med WORM-opbevaring (fx S3 Object Lock i compliance mode, som ikke engang root-kontoen kan forkorte), hærdede Linux-repositorier med immutable-flag på filerne, bånd, der roteres ud af huset, og backupsystemer i et separat administrativt domæne med egne MFA-beskyttede konti. Snapshots på samme storage-system, RAID og synkron replikering er ikke backup: de gengiver trofast sletning, korruption og kryptering.\n\nKonsistens er lige så vigtig som eksistens. Et crash-konsistent image af en kørende database starter måske ikke; applikationskonsistente backups fastfryser skrivninger (på Windows via VSS-writers) eller bruger databasens egen dump- eller logmekanisme. SaaS-data er et hyppigt hul - under modellen for delt ansvar garanterer udbydere som Microsoft 365 tjenestens tilgængelighed, men tilbyder kun begrænset opbevaring af data, som brugere har slettet eller angribere har ændret.\n\nNormative ankre: CIS Controls v8 Control 11 (Data Recovery), herunder en isoleret kopi af gendannelsesdata (Safeguard 11.4) og gendannelsestest af et udsnit af aktiverne mindst kvartalsvist (11.5); ISO/IEC 27002:2022 kontrol 8.13 (backup af information); NIS2 art. 21, stk. 2, litra c, der nævner backupstyring sammen med driftskontinuitet og katastrofeberedskab; og databeskyttelsesforordningens art. 32, stk. 1, litra c, om evnen til rettidigt at genoprette tilgængeligheden af og adgangen til personoplysninger. Opbevaringen har også en databeskyttelsesside: backups med personoplysninger er omfattet af princippet om opbevaringsbegrænsning, og anmodninger om sletning håndteres typisk ved dokumenteret udløb frem for ved at redigere gamle backupsæt. Det eneste reelle bevis på, at en backup virker, er en tidsmålt og dokumenteret gendannelse."},"edges":[{"type":"kind-of","to":"security/control","confidence":"high","strength":"normal"},{"type":"mitigates","to":"security/ransomware","why":{"en":"With a clean copy stored apart, locked data can be restored without paying.","da":"Med en ren kopi opbevaret separat kan låste data gendannes uden at betale."},"confidence":"high","strength":"primary"},{"type":"used-with","to":"security/disaster-recovery-plan","confidence":"high","strength":"normal"},{"type":"used-with","to":"security/business-continuity-plan","confidence":"high","strength":"normal"},{"type":"used-with","to":"security/recovery-objectives","confidence":"high","strength":"normal"},{"type":"used-with","to":"cs/database","confidence":"high","strength":"normal"}],"depth":0,"sources":[{"title":"Cyber Security Fast Track - Ordliste","tier":"course-material"},{"title":"CIS Critical Security Controls v8 - Control 11 (Data Recovery)","tier":"standard","publisher":"Center for Internet Security"}],"draft":true}